function validate_callback()
{
    var Name	 		= document.callback.Name;
    var Email	 		= document.callback.Email;
    var Tel	 			= document.callback.Tel;
    var Enquiry	 		= document.callback.Enquiry;
    var update    		= document.callback.update.value == "True";

 


    if (Name.value == "")
    {
        window.alert("Please enter your Name.");
        Name.focus();
        return false;
    }  
      
    if (Email.value == "")
    {
        window.alert("Please enter a valid e-mail address.");
        Email.focus();
        return false;
    }
    
    if (Email.value.indexOf("@", 0) < 0)
    {
        window.alert("Please enter a valid e-mail address.");
        Email.focus();
        return false;
    }
    
    if (Email.value.indexOf(".", 0) < 0)
    {
        window.alert("Please enter a valid e-mail address.");
        Email.focus();
        return false;
    }
    
        if (Tel.value == "")
    {
        window.alert("Please enter your contact number.");
        Tel.focus();
        return false;
    }  


   if (Enquiry.value == "")
    {
        window.alert("Please enter your Enquiry");
        Enquiry.focus();
        return false;
    }
         
	 return true;
	   }