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;
}      
//Usage: Insert the following line in the textfield declaration syntax
//     onKeyPress="return numbersonly(this, event)"
//--------------------------------------------------------------------