var NumericForm = {
    init: function() {
        var inputs = document.getElementsByTagName("input");
        for (var i = 0; i < inputs.length; i++){
            var input = inputs[i];
            if (input.getAttribute && input.getAttribute("numericform")){
                input.value = add_comma(input.value);
                Event.observe(input, 'focus', NumericForm.formfocus, true);
                Event.observe(input, 'blur', NumericForm.formblur, true);
            }
        }
    },

    formfocus: function(event) {
        var input = Event.element(event);
        input.value = remove_comma(input.value);
        input.select();
    },

    formblur: function(event) {
        var input = Event.element(event);
        input.value = add_comma(input.value);
    }
}

Event.observe(window, 'load', NumericForm.init, false);