CRM Workflow Input box on Rejection of BP

Hello,

I created 2 Level Custom Workflow for a New BP Approval from CRM Screen.

In approval process, when the manager gets the screen for decision - Approval / Rejection, Once the

manager selects Reject and input box for mandatory rejection text is required.

I created an implicit enhancement for input box using FM 'POPUP_GET_VALUES', this works well in ERP ( SBWP). But no input box is displayed for input in CRM Screen.

Can some1 please help how to proceed ?

Thanks & Regards,

Narendra.