Transaction code OP5A - fields control by Plant and Transaction code

Dear Experts,

Currently the user creates and modifies task list for PP without change number control. Now, we need that the field change number be mandatory for transactions CA01 and CA02 and for one specific plant too.

I am trying to use the transaction code OP5A but there is not working using the influence fields. Do you know if it is possible to have more than one influences for transaction code CA01 and CA02 by plant? I mean, the field change number must be mandatory just when the user access the transaction codes CA01 and CA02 for plant XYZ.

My steps are below to clarify what I did:

1 - transaction OP5A;

2-  doble click in PP task list: initial screen;

3 - doble click Modification Number field;

4 - Click in Plant>New values>Inform the plant code>flag mandatory field;

5 - Clicl in Transaction>New values>inform the transaction CA01 and transaction CA02>mandatory for both transaction

Please let me know if you need more detail.

I hope you have a great weekend,

BR

Valdevair