javascript to change group name

change group name :

<script language="javascript" type="text/javascript">

function changeValidationGrop(){

var btn = document.getElementById("<%=Button1.ClientID %>");

//rfvUsername = document.getElementById("<% = rfvUsername.ClientID %>");

//rfvUsername.ValidationGroup = "Demo";

//alert(rfvUsername.ValidationGroup);

btn.onclick = function(){

WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions("Button1", "", true, "Customer", "", false, false));

}

}

<script>