Hi Cha,
You can go to the Sales area data view which i think in this case is BP_SALES/CorpAccountSalesAreasOV. Then the code to show button is in DO_PREPARE_OUTPUT of the implementation class of view.
Enhance the component ( If not enhanced ) & then Enhance the view. Then Redefine DO_PREPARE_OUTPUT & comment the button logic.
Regards,
Ravi