เลือกข้อมูลใน list menu แล้วให้ข้อมูลโชว์ใน text box อัตโนมัติ

<select name="listmenu2" title="รายการสินค้า" class="style5" onchange="frmMain.txtVol.value=this.value">
        <?
	require("../../config/config.inc.php");
	$sql = "select * from table_name where อะไรก็ว่าไปครับ ";
	$first="";
	$result = mysql_query($sql,$dbcon);
	$array= mysql_fetch_array($result);
			if(!$first){ $first=$array[id]; }
	echo "<option class=style6  value=$array[id]>$array[name]</option>";
	
	$sql= "เหมือนข้างบนแล้วแต่จะสร้าง";
	$result=mysql_query($sql,$dbcon);
		while($array = mysql_fetch_array($result))
	{				if(!$first){ $first=$array[id]; }
				echo "<option value =$array[id]>";
				echo " $array[name]<br>";
	}
	?>
     </option></select><input type="hidden" name="txtVol" value="<?=$first?>"/>

<?
       include('connect.php');
	  $sql_itemno = "select ITEM_NO,ITEM_NAME from item ";
	  $result_itemno = mysql_query($sql_itemno) or die ("Error Query [".$sql_itemno."]");                  ;
     ?>
        <select name="lstItemno" size="1" id="select" onchange="show(this.value);">
          <?php
		  ?>
		  <option value=""> ====> Select Item No<===== </option>
		  <?
while($result = mysql_fetch_array($result_itemno ))
{
?>
          <option value="<?=$result["ITEM_NO"];?>"><?=$result["ITEM_NO"];?>
          </option>
          <?
}
?>
        </select>

	var myStr = val ;
	var mySplitResult = myStr.split(",");
	for(i = 0; i < mySplitResult.length; i++)
	{
	document.forms.frmMain.TproCatid.value = mySplitResult[0];
	document.forms.frmMain.TproCatname.value = mySplitResult[1];
	}

<select name="selectcat" id="selectcat" style="width:24px;" onChange="JavaScript:sel(this.value)"><option value="<?=$objResuut["categoryid"];?>,<?=$objResuut["categoryname"];?>"><?=$objResuut["categoryid"]." - ".$objResuut["categoryname"];?></option>
<?
			$strSQL = "SELECT * FROM category ORDER BY categoryid ASC";
			$objQuery = mysql_query($strSQL);
			while($objResuut = mysql_fetch_array($objQuery))
			{
?>
		  <option value="<?=$objResuut["categoryid"];?>,<?=$objResuut["categoryname"];?>"><?=$objResuut["categoryid"]." - ".$objResuut["categoryname"];?></option>
<?
			}
?>
      </select>