function AllowAlphaNumericOnly(){ 
    Expression = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'; 
    var ch = String.fromCharCode(window.event.keyCode); 
    ch = ch.toUpperCase(); 
    var a = Expression.indexOf(ch); 
    if (a == -1)  
        window.event.keyCode = 0; 
 }
 
 function AllowNumericOnly(){ 
    Expression = '0123456789'; 
    var ch = String.fromCharCode(window.event.keyCode); 
    ch = ch.toLowerCase(); 
    var a = Expression.indexOf(ch); 
    if (a == -1)  
        window.event.keyCode = 0; 
 }