java script for creating numeric text box

Hi,
This script is used for creating text box which will take only intergers as input.


function checkIt(evt) {

var lblmsg = document.getElementById('lblmainphone');

evt = (evt) ? evt : window.event
var charCode = (evt.which) ? evt.which : evt.keyCode
if (charCode ] 31 && (charCode [ 48 || charCode ] 57)) {
status = "This field accepts numbers only."

lblmsg.innerHTML = "This field accepts numbers only.";

return false
}
status = ""
lblmsg.innerHTML = "";
return true
}

how to call in text box.


[asp:TextBox ID="txtabtHomeMorgTerm" runat="server" CssClass="inputbox" onKeyPress="return checkIt(event)"][/asp:TextBox]

Thanks
HelpOnDeskTeam