Validating before Checkout

[kfchoong]

Hi,

 

I would like to perform some validating after the purchase of Product/Service before checkout is completed. If I were to add a hook (ShoppingCartValidateCheckout), is it possible to call a customized page from within the hook? Also, from the documentation, it says "runs when checkout is clicked, can use global $errormessage to pass back error", how do I pass the errormessage from within the hook? Can anyone point me to some sample codes as I couldn't find any from the documentation.

 

Thanks.