Javascript code:
 
function
isNumeric()
{
if(((window.event.keyCode
>= 48) && (window.event.keyCode
<= 57)) || ((window.event.keyCode >= 96)
&& (window.event.keyCode <= 105)) ||
((window.event.keyCode == 8) || (window.event.keyCode == 9) || (window.event.keyCode == 46) || (window.event.keyCode == 35) || (window.event.keyCode == 36) || (window.event.keyCode == 37) || (window.event.keyCode == 39)))
      {
            return
true;                        
      }
      else
      {
            return
false;
      }
}