Product substitution in APO

I am in SCM 4.1 and I defined a product interchangeability in the transaction /INCMD/UI.

Sould I define this product substitution also in SAP R/3 ?

In the substitution, I defined product A substituted by product B. I have a planned order where I have the product A. When I convert this planned order to production order, normally if I understood well the system should replace automatically the product A by the product B and it is not the case. I have an error in the CIF "Screen output without connection to user".

Can someone help me ?

Thank you in advance.

Isabelle Eustache.