function isNumber(e){    
    var isNumber;
    if (window.event)key = window.event.keyCode;
    else if (e) key = e.which;
    else isNumber = true;
    keychar = String.fromCharCode(key);

    // control keys
    if ((key==null) || (key==0) || (key==8) || 
        (key==9) || (key==13) || (key==27) )
       isNumber = true;

    // numbers
    else if ((("0123456789").indexOf(keychar) > -1)) isNumber = true;
    else isNumber = false;
       
    return isNumber
}