function ValidateEmail(emailTxtbx, noEntryError, invalidEmailError) {
    var emailText = document.getElementById(emailTxtbx);
    if(emailText != null && emailText.value != "") {
        var apos = emailText.value.indexOf("@");
        var dotpos = emailText.value.lastIndexOf(".");
        if (apos < 1 || dotpos-apos < 2) 
        { alert(invalidEmailError); emailText.focus(); return false; }
        else {return true;}
    } else { alert(noEntryError); emailText.focus(); return false; }
}