function _submit(ds_copy){
	document.getElementById('ds_copy').value=ds_copy;
	document.getElementById('fm').submit();	
}

function _submit(ds_copy){
	document.getElementById('fm').submit();	
}

<script language="JavaScript">
<!--
function _submit(ds_copy){
	document.getElementById('ds_copy').value=ds_copy;
	document.getElementById('fm').submit();	
}

//-->
</script>
...
<form method="post" action="{$SCRIPT_NAME}" name="fm" id="fm">
<input type="hidden" name="ds_copy" id="ds_copy" value="{$ds_copy}">
...
<td onClick="javascript:_submit(0);">Data</td>
...
</form>

alert(document.getElementById('ds_copy').value);