Hey @MR1 

Oopss! Seems I was missing one line.

function onSubmit() {

    /*** Pop this gem into your script! */
    if (g_scratchpad.isFormValid) {
        return true;
    }
    var actionName = g_form.getActionName();
    var business = g_form.getReference('resource_group_to_be_updated', getValue);
    return false; //this line was missing

    function getValue(business) {
        if (business.manager.toString() == '') {
            alert('Order Now is disabled if the assignment group manager is empty');
            return false;
        }
		g_scratchpad.isFormValid = true;
		g_form.submit(actionName);
    }
}

Cheers,

Tai Vu