i shift value from list to rich textarea in specified position but it does not work for
document.selection .it produced undefined value so it can't go in loop
following is my function
my browser is Netscape and version>4

function shiftvalue(frm)
{

if(document.frm.columnName.value=="")
{
alert("Please Select Mail Parameter");
return false;
}
else
{
var tn=document.frm.dsrte_text;

var shiftValue = frm.columnName.options[frm.columnName.selectedInde
x].value;
alert(shiftValue);
//IE support
if (document.selection)
{

tn.focus();
sel = document.selection.createRange();
sel.text = shiftValue;
alert(sel.text)
}
//MOZILLA/NETSCAPE support
else if ((tn.selectionStart == 0) && (tn.selectionEnd == 0))
{
tn.value += shiftValue;
alert(tn.value);
}
else
{

var startPos = tn.selectionStart;
var endPos = tn.selectionEnd;
tn.value = tn.value.substring(0, startPos) + " " + shiftValue + " " + tn.value.substring(endPos, tn.value.length);

}
return false;
}
}


here i call that function
<input type="button" name="btnShift" value="<<" onclick="return shiftvalue(this.form);" >