Profit Center as mandatory field for Posting keys 01, 11, 31, etc.

Hello,

Currently I am in a project in which we have implemente New GL; my client is asking me to activate the Profit Center field for posting keys 01, 11, 21 and 31, so they can post in example documents with posting key 31 (vendor) vs posting key 01 (client). I modified the accounts field status in order for the Profit Center to be mandatory. I modified, as well, posting keys 01, 11, 21 and 31 field status' in orden for the profit center to be mandatory as well. Regardless of this, the profit center just doesn't appear when I post a document in example through tx F-02.

Does anyone knows how to make this field appear for the posting keay I mentioned? Is it possible? or is this a system limitation?

Thanks in advance for your help.

Regards,

HP