สอบถามเรื่อง การคำนวนหลายเงื่อนไขใน textbox php ค่ะ

<script language="javascript" type="text/javascript">  
function useif(){ 
var a1 = document.frmMain.txtstd_wh.value; 
var a = document.frmMain.txttype_code.value;
var b=document.frmMain.suppweight_total.value; 
var c=parseFloat(document.frmMain.pack_qty.value);     
var d=document.frmMain.txtpk_weight1.value;
var e=document.frmMain.off_total.value;
if(a=="STD-P"){ 
document.frmMain.std_pur.value=(c-d)*c;
}else if(a=="ENT-P"){
document.frmMain.std_pur.value=(b-d)*c;
}else if(a=="DES-P"){
document.frmMain.std_pur.value=(e-d)*c;
}else if(a=="STD+P"){ 
document.frmMain.std_pur.value=(c-d)*c;
}else if(a=="ENT+P"){
document.frmMain.std_pur.value=(b-d)*c;
}else if(a=="DES+P"){
document.frmMain.std_pur.value=(e-d)*c;

}
}  
</script> 
<script language="javascript" type="text/javascript">  
function use(value){  
var a1 = document.frmMain.txtstd_wh.value;
var b1=document.frmMain.suppweight_total.value; 
var c1=parseFloat(document.frmMain.pack_qty.value);     
var d1=document.frmMain.txtpk_weight1.value;
var e1=document.frmMain.off_total.value;
if(a1=="STD-P"){ 
alert(e1);
document.frmMain.std_wh.value=(c1-d1)*c1;
}else if(a1=="ENT-P"){
alert(value);
document.frmMain.std_wh.value=(b1-d1)*c1;
}else if(a1=="DES-P"){
alert(value);
document.frmMain.std_wh.value=(e1-d1)*c1;
}else if(a1=="STD+P"){ 
alert(value);
document.frmMain.std_wh.value=(c1-d1)*c1;
}else if(a=="ENT+P"){
alert(value);
document.frmMain.std_wh.value=(b1-d1)*c1;
}else if(a1=="DES+P"){
alert(value);
document.frmMain.std_wh.value=(value-d1)*c1;
} 
}  
</script> 

  <input name="suppweight_in" type="text" size="15" value="<?=$objResult["suppweight_in"];?>"  onKeyUp="chk()" <?=$text?>/></label>
                <lable>&nbsp;&nbsp;out:
                <input name="suppweight_out" type="text" value="<?=$objResult["suppweight_out"];?>"  size="15"  onKeyUp="chk()" <?=$text?>/></label>
                <lable>
                &nbsp;&nbsp;Sup Net:
                <input name="suppweight_total" id="suppweight_total" type="text" value="<?=$objResult["suppweight_total"];?>"  size="15" onchange="useif()" readonly/></label> <input name="suppweight_total2" id="suppweight_total2" type="hidden"  size="15" onchange="useif()"/>               </td>
              </tr>
	     <tr>
              <td height="23" colspan="2" bgcolor="#006699" class="style6" >Office Weight </td>
              </tr>
            <tr>
              <td height="38" colspan="2" class="style5" >&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;IN:
                <label>
                <input name="off_in" type="text" size="15" value="<?=$objResult["off_in"];?>" onKeyUp="chk2()" <?=$text?>/></label>
                <lable>&nbsp;Out:
                <input name="off_out" type="text" size="15" value="<?=$objResult["off_out"];?>" onKeyUp="chk2()"  <?=$text?>/></label>
               <lable> &nbsp;&nbsp;&nbsp;Diff:
                <input type="text" name="off_total" id="off_total" value="<?=$objResult["off_total"];?>" OnKeyUp="use(this.value);"  readonly/></label><input type="text" name="off_total2" id="off_total2" <?=$text?>/>                </td>
              </tr>
            <tr>
              <td height="23" colspan="2" bgcolor="#006699" class="style6" >Supplier Package </td>
              </tr>
            <tr>
              <td height="68" colspan="2" valign="top" class="style5" >&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Pack Qty: 
                <label>
                <input name="pack_qty" type="text" size="15" value="<?=$objResult["pack_qty"];?>"  onkeyup="chk4()" onkeypress="useif()" onchange="use()" <?=$text?>/>
                &nbsp; </label><lable>
                <input name="txtpack_name1" type="text" id="txtpack_name1" size="15" value="<?=$objResult["pack_name"];?>" onchange="use()" readonly/> </label>
                <br />
                <label>&nbsp;&nbsp;&nbsp;Package Weight/Unit: 
                <input name="txtpk_weight1" type="text" id="txtpk_weight1" size="10" value="<?=$objResult["pk_weight"];?>" onkeyup="chk4()" readonly/></label>
                <br />
                <lable>&nbsp;&nbsp;&nbsp;Product Weight/Unit:
                <input name="txtweight1" type="text" id="txtweight1" size="15" value="<?=$objResult["weight"];?>" readonly/></label>
                <lable><input name="pd_weight" type="text" size="15" value="<?=$objResult["pd_weight"];?>" <?=$text?>/></label>
                </label></td>
              </tr>
           
            <tr>
              <td height="21" colspan="2" bgcolor="#006699" class="style6" >Standard Weight </td>
              </tr>
            <tr>
              <td height="38" colspan="2" class="style5" >&nbsp;&nbsp;&nbsp;STDPUR : 
                <label>
                <input name="std_pur" type="text" size="15" value="<?=$objResult["std_pur"];?>"  onfocus="chk3()" <?=$text?>/></label>
                <lable>
                &nbsp;&nbsp;STD WH :
                <input type="text" size="15"  name="std_wh" value="<?=$objResult["std_wh"];?>"  onfocus="chk3()" <?=$text?>/></label> 
<lable>
&nbsp;&nbsp;Office Net : 
<input name="std_weightdiff" type="text" value="<?=$objResult["std_weightdiff"];?>" size="15" readonly/>