Cause Postback from Javascript

<input type="button" id="Button2" value="Press me" onclick="DoPostBack()" />
<script language="javascript" type="text/javascript">
 
function DoPostBack() 
{
  __doPostBack('Button2','My Argument');     
}
 
</script>
string passedArgument = Request.Params.Get("__EVENTARGUMENT");