[TYPO3-commerce] Using Hooks with no return value

[Christopher Schnell]

Hi all,
this is my first "hooked" extension, so please be kind :-)

I added a class to the hook 
['commerce/pi3/class.tx_commerce_pi3.php']['canMakeCheckout'] and 
implemented the method canMakeCheckoutOwnTests($checks,$myCheck).
The class and method get called and I can check, if a certain minimum 
value (of money) is in the basket. But I do not know how to return this 
error-value to the main class, since the extension class is called with 
$hookObj->canMakeCheckoutOwnTests($checks,$myCheck);

What do I do with the hookObj or how can I influence, if a user cannot 
check out.

I hope, I could explain, what my problem is.

Thanks for help,
Regards.
Christopher.