/* Only allow numbers in the given field */
function numbersonly(myfield, e, dec) {
    var key;
    var keychar;

    if (window.event) {
        key = window.event.keyCode;
    } else if (e) {
        key = e.which;
    } else {
        return true;
    }

    keychar = String.fromCharCode(key);

    // control keys
    if ((key==null) || (key==0) || (key==8) || (key==9) || (key==13) || (key==27)) {
        return true;
    }
    // numbers
    else if ((('0123456789.').indexOf(keychar) > -1)) {
        return true;
    }
    // decimal point jump
    else if (dec && (keychar == '.')) {
        myfield.form.elements[dec].focus();
        return false;
    } else {
        return false;
    }
}