Managing package and products

[Jull]

Hi everybody !

I sell 2 differrents produts, in 2 differrents way : One by One or by package with the 2 products.

When a customenr buy only one product the number of package available does not decrease.

Ex :
5 products A
5 products B
5 packs can be made

If a customer buy only the product A, from my point of view the result must be :

4 products A
5 products B
4 packs can be made

But the result is :

4 products A
5 products B
5 packs can be made

How i must proceed to get this target .


Merci !