function doNext(el)
{
    if (el.value.length < el.getAttribute('maxlength')) return;

    var f = el.form;
    var els = f.elements;
    var x, nextEl;
    for (var i=0, len=els.length; i<len; i++) 
    {
        x = els[i];
        if (el == x && (nextEl = els[i+1])) 
        {
            if (nextEl.focus) nextEl.focus();
        }
    }
}


function onlyNumbers(e)
{
    var keynum;
    var keychar;
    var numcheck;

    if(window.event) // IE
    {
        keynum = e.keyCode;
    }
    else if(e.which) // Netscape/Firefox/Opera
    {
        keynum = e.which;
    }
    keychar = String.fromCharCode(keynum);
    numcheck = /\d/;
    return numcheck.test(keychar);
}