update customer group when order confirmed

-- url of the page with the problem -- : mywebsite.com/mypage
-- HikaShop version -- Business
-- Joomla version -- :2.5.9
-- PHP version -- : x.x.x
-- Browser(s) name and version -- : XXXXX x.x.x
-- Error-message(debug-mod must be tuned on) -- : Error_message

Hello,
depending on the type of product my clients buy, I would like to assign them to specific user_groups that I created. (I use then the user_groups to let them access to different part of the site).
I am looking for the functions/files where, when the order is confirmed, we write in the sql table hikashop_order. Then I could add a few lines to write also in the user_usergroup table of joomla (hopefully in this function/file I have access to the user_id).
Could you please tell me where I can find these functions/files or/and if I am looking at the right method to do that (and if there is a better alternative).

Hi,
Note that the solution will probably be to use the "User group after purchase" option through your product configuration page.

fantastic, so smart and simple!!!!
thank you