Hi Mike/Zarina,
The feild change need to be done in V_T588M module pool mp008800.
the correct screen to be maintained is as follows:-
screen variable key alternative screen next screen
2000 STPA 2011 0
2000 STPB 2021 0
ALso please apply SAP note 1559563 changes in your system.
This should resolve the isuse.
Reward points if it is resolved.
Regards,
Shobha Singajogi