Add a new task to the cart controller

[j.pereira.araujo]

Hi there.
I have a problem that's been troubling for a long time.
I have installed Joomla 2.5 with virtuecart 2.0.6, and I created a new button in the checkout phase, but I like to trigger a new "task", so I can make some changes in my database, and I tried give a diferent name (JRoute) but when i echo in the virtuemart.php it fires the controller (cart.php) but the task doesn't show.
I tried the registerTask also but it seems not to work. Where is the tasks for the cart controller being created? And how it works the mapping?
Thanks in advance.
João Araújo.