multiple selection using combobox

[anju07]

hi,
I have a combo-box, in which ive set its MULTIPLE attribute.
But, as i select an option i want it to appear in a textbox,comma-separated.
How can i acheive that?

[iam_clint]

Example provided below.

<script>
var i = 0;
function Delim(){
   var obj = document.getElementById("sel1");
   var opts = obj.options;
   var sVal = "";
   var tVal = "";
   for (i=0; i<opts.length; i++)   {
	if (opts[i].selected == true) { sVal += opts[i].innerHTML+","; tVal += opts[i].value+","; }
   }
  var text1 = document.getElementById("sVal");
  var text2 = document.getElementById("tVal");
  text1.value = sVal;
  text2.value = tVal;
}
function wait() {
 window.setTimeout("Delim()", "100");
}
</script>
<input type="text" id="sVal"><input type="text" id="tVal">
<br>
<select name="sel1" id="sel1" onclick="wait();" style="width: 310px;" multiple>
<option value="1">blah</option>
<option value="2">blah1</option>
<option value="3">blah2</option>
<option value="4">blah3</option>
<option value="5">blah4</option>
<option value="6">blah5</option>
<option value="7">blah6</option>
<option value="8">blah7</option>
<option value="9">blah8</option>
<option value="10">blah9</option>
<option value="11">blah10</option>
<option value="12">blah11</option>
<option value="13">blah12</option>
<option value="14">blah13</option>
<option value="15">blah14</option>
<option value="16">blah15</option>
<option value="17">blah16</option>
<option value="18">blah17</option>
<option value="19">blah18</option>
<option value="20">blah19</option>
<select>