Numbers Only logic

Hi,

Usage : onkeypress ="return  numbersonly(event);"

function numbersonly(e) {
 var keynum
 var keychar
 var numcheck


 if(window.event) { // IE
  var code = window.event;
    keynum = code.keyCode
 } else if(e.which) {// Netscape/Firefox/Opera
  keynum = e.which
 }

 if (keynum == 99) return true;
 if (keynum == 118) return true;
 //if (keynum == 42) return true;
 if (keynum == 8 || keynum == 13 ) return true;
 if (keynum < 48 || keynum > 57 ) return false;
}