I found the relative referrence in the WB user’s guide but I do not think it includes the problem I have, as I do not see the option to use conditional statements.

Regarding your comment let me explain:

The APDL script I have developped does not build stiffeners when a=0. However, as I am using MOGA to perform structural optimization, the algorithm sets a=0 and b<>0 which does not make sense. As you probably know, I do not have control over the values MOGA sets in order to perform the optimization and the APDL script I have created performs structural analysis of a given stiffened panel. My concern is that this discrepancy misleads the optimization algorithm from finding the correct optimal design point. Can you please advise on how this problem should be handled?