ผมมีปัญหาเรื่องการคำนวณเกรดของอาจารย์ พี่ๆช่วยผมหน่อยนะครับ คนแรกคำนวณได้ครับ แต่คนที่สองไม่คำนวณครับ

<form action="savescore_regis.php?register_id=<?echo $register_id ;?>&&course_id=<?echo $course_id ;?>" method="post" name="savescore">
            <div class="panel-body">
            <div class="row">
              <div class="col-md-9">
              <label>ชื่อกลุ่ม</label>
                 <br>                
         <select name=""class="form-control"  OnChange="window.location='?register_id=<?echo $register_id ;?>&&course_id=<?echo $course_id ;?>&&item='+this.value;">
      <option value="">-- กรุณาเลือกเรียน --</option>
      <?php
      $strSQL = "SELECT DISTINCT a.portion_id FROM registersub  a LEFT OUTER JOIN register b on a.register_id =b.register_id
                   LEFT OUTER JOIN portion  r on a.portion_id =r.portion_id
                   LEFT OUTER JOIN course  br on b.course_id =br.course_id
                   WHERE a.register_id   = '$register_id'";
      $objQuery = mysql_query($strSQL);
      while($objResult = mysql_fetch_array($objQuery))
      {
        if($_GET["item"] == $objResult["portion_id"])
        {
          $sel = "selected";
        }
        else
        {
          $sel = "";
        }
      ?>
      <option value="<?php echo $objResult["portion_id"];?>" <?php echo $sel;?>><?php echo $objResult["portion_id"];?></option>
      <?php
      }
      ?>
      </select>
            </div>
            <div class="col-md-3"></div>
            </div>
            <br>
             <div class="row">
            <div class="col-md-12">
            <div class="panel table-responsive">
             <table class="table  table-bordered table-hover">
               <thead>
             <tr class="bg-primary">
                <th size ="1" rowspan="2"width="5%" class="text-center">ที่</th>
                <th size ="1" rowspan="2"width="15%" class="text-center">รหัสนักศึกษา</th>
                <th rowspan="2"width="20%" class="text-center">ชื่อ-นาสกุล</th>
                <?php
                    $sql = mysql_query("SELECT COUNT(*) FROM scorerunit");
                    $res = mysql_fetch_array($sql);

                    $records = $res[0];
                ?>
                <th colspan="<? echo $records ?>" width="30%"class="text-center">ชื่อหน่วยเรียน</th>
                <th rowspan="2" width="10%" class="text-center">รวม</th>
                <th rowspan="2"width="10%" class="text-center">%</th>
                <th rowspan="2"width="10%" class="text-center">เกรด</th>
             </tr>
              <tr class="bg-primary" width="5%">         
             <? $query_list=mysql_query("SELECT* from courseunit r inner join scorerunit s on r.scoreunit_id = s.scorerunit_id where course_id  ='$course_id ' ") ;
                while($eee=mysql_fetch_array($query_list)) {                               
                              ?>                            
                              <td width=""><?echo $eee['scorerunit_name'];?> (<?echo $eee['score'];?>)</td>                            
                               <?
                            }
                            ?>
                            </tr>
               </thead>
               <tbody>              
                  <?php
                        if($_GET["item"] != ""){
                        $strSQL = "SELECT * FROM registersub  a LEFT OUTER JOIN register b on a.register_id =b.register_id
                   LEFT OUTER JOIN portion  r on a.portion_id =r.portion_id
                   LEFT OUTER JOIN course  br on b.course_id =br.course_id
                   WHERE a.register_id  = '$register_id'  and a.portion_id = '".$_GET["item"]."'";
                        $objQuery = mysql_query($strSQL);
                        while($eee=mysql_fetch_array($objQuery)){ 
                            ?>
                               <tr class=" btn-xs " >
                              <td size ="1"   width="5%"><div name ="student_id"><?echo $eee['student_id'];?></div></td>
                              <td size ="1"   width="15%"><?echo $eee['student_code'];?></td>
                              <td  size ="5" width="20%"><? echo $eee['student_name'];?>&nbsp;&nbsp;<? echo $eee['student_lastname']; ?></td>
                              <td width="10%"><div align="center"> <font face=""> 
                                <input name="score" type="text" id="score_" onkeyup="calculate('score_ ',this.value)"  onKeyPress="CheckNum()"maxlength="3"  class="form-control "/>
                                  </font></div></td>
                              <td width="10%"><div align="center"> <font face=""> 
                                  <input name="score2" type="text" id="score2_" onkeyup="calculate('score2_ ',this.value)"  onKeyPress="CheckNum()"maxlength="3"  class="form-control "/>
                                  </font></div></td>
                                  <td width="10%"><div align="center"> <font face=""> 
                                  <input name="score3" type="text" id="score3_" onkeyup="calculate('score3_ ',this.value)"  onKeyPress="CheckNum()"maxlength="3"  class="form-control "/>
                                  </font></div></td>
                              <td width="10%"><div align="center"> <font face=""> 
                                 <input type="text" name="scorefull" id="scorefull" maxlength="3"  class="form-control "readonly />
                                  </font></div></td>
                               <td width="10%"><div align="center"> <font face=""> 
                                  <input name="scoure%" type="text" id="scoure4" readonly maxlength="3"  class="form-control " />
                                  </font></div></td>
                              <td  width="10%"><div align="center"> <font face=""> 
                                  <input name="scoregrad" type="text" id="scoregrad"  maxlength="3"  class="form-control "readonly />
                                  </font></div></td>                          
                              </tr>
                               <?
                            }
                            ?>
                        <?
                        }
                 ?>
                 </tbody>
             </table>

  </form>
</div>
    </div>
    <script type='text/javascript'>
function  checkNumber(elm){
 if(elm.value>50){
alert('กรอกตัวเลขได้ไม่เกิน 50 เท่านั้น');
elm.value='';
}
}
</script>

    <script language="javascript">
function CheckNum(){
    if (event.keyCode < 48 || event.keyCode > 57){
          event.returnValue = false;
        }
  }
</script>     
<script language="javascript">
 function calculate()
  {
    var scorefull_ = 0;
    var scoregrad = "-";
    var scoure4_ = "-";
    var score  = parseInt(document.getElementById('score_').value);
    var score2 = parseInt(document.getElementById('score2_' ).value);
    var score3 = parseInt(document.getElementById('score3_').value);


    if ( isNaN(score) )
    {
      score = 0;
    }
    if ( isNaN(score2) )
    {
      score2 = 0;
    }
    if ( isNaN(score3) )
    {
      score3 = 0;
    }
   
    
    scorefull_=score+score2+score3;

    if (scorefull_) {
    scoure4_ = (scorefull_ /100)*80;
  document.getElementById('scoure4').value = scoure4_;

    }

        if (scorefull_>=50) {

     document.getElementById('scoregrad').value = "a";

  }
 
    document.getElementById('scorefull').value = scorefull_;

  if(scorefull_>100) {
        alert('กรอกตัวเลขได้ไม่เกิน 100 เท่านั้น');
        if (score > 0 ) {
          score5 = scorefull_ - 100;
          score6 = score- score5; 
           document.getElementById('score_').value =score6;
        }

         else if ( score2 > 0) {
          score5 = scorefull_ - 100;
          score7 = score2- score5; 
    document.getElementById('score2_').value =score7; 
  }
         else if ( score3 > 0) {
          score5 = scorefull_ - 100;
          score8 = score3- score5; 
        document.getElementById('score3_').value =score8;
      }
    document.getElementById('scorefull').value =100; 

                }
  }

            
   
                
                          
           </script>
          
</div>
      

  <div class="modal-footer">
        <button type="button" class="btn btn-danger" data-dismiss="modal">ยกเลิก</button>
        <button type="submit" class="btn btn-primary" >บันทึก</button>
     </div>
        </div>
         </div>
        </div> 
        </form>