function CheckNumeric() {
    //Allows only numeric characters using the keypress event

    // Get ASCII value of key that user pressed
    var key = window.event.keyCode;

    // Was key that was pressed a numeric character (0-9) ?
    // note if want to add a 'minus' sign, also allow key 45
    if ((key > 47 && key < 58))
        return; // if so, do nothing
    else
        window.event.returnValue = null; // otherwise, discard character
}