Append/Move to List from List

<script type='text/javascript'>function append (frm) {
s1 = frm.elements['skills[]'];
s2 = frm.elements['selSkills[]'];
b = false; s1Index = s1.selectedIndex; 

val = s1.options[s1Index].text; // current value of s1
c = s2.length; // current value of select 2 

if (c > 0)  {
// loop s2, check if already added  

for (i=0; i < c; i++)  {
 if (val == s2.options[i].text)
 b = true; // matched, no addition
 }

 if (b == false)  {
  op = new Option(val);
  s2.options[c] = op; // add option to s2
 }
 else {
  alert('Already added.');
 }
}
else {
 op = new Option(val);
// assign to left list
s2.options[c] = op;
}
}

function clr (frm) {
theList = frm.elements['selSkills[]'];
 itemNo = theList.selectedIndex;
 if (itemNo != -1)     

theList.options[itemNo] = null;
 }
</script>

<form method="post">
<select size='4' name='skills[]' ondblclick='javascript:append(this.form)' title='double click to select'>
<option value='PHP'>PHP</option>

<option value='MySQL'> MySQL </option>
<option value='ApacheConf'> ApacheConf </option>
<option value='Javascript'> Javascript </option>
<option value='CSS'> CSS </option>
<option value='HTML'>HTML</option>
</select>

<input type="button" onclick="javascript:append(this.form)" value=">>"title='select/move to left' />

<select name='selSkills[]' multiple></select>
<input type='button' name='clear' value='Clear' onclick='clr(this.form)' title='clear list' />

</form>