Select quantity for pack products

[gift]

Hi, I'm new for prestashop, and would like some help for this problem.

 

I do the shop about shirt and 1 of product have to sale in pack.

 

For example I have 2 type of shirts and can choose 5 shirts in one pack (all have to be same size)

so if customer pick

- shirt A for 4, and force shirt B have to 1 shirt or

- shirt A for 2, shirt B have to 3 shirts

(as the attached image)

 

how can I do like this, please give me some advise

Thank you very much

Edited June 4, 2013 by gift (see edit history)