Creating an Excel upload fucntionality from custom button from NWBC in SAP TM

Hi

I have a requirement of creating a UPLOAD FROM EXCEL from presentation server using a custom button in the toolbar from NWBC in SAP TM . I have created this button in the toolbar in a custom tab and assigned an action class to it. I tried using the standard GUI_UPLOAD that we normally use for ABAP but it is giving me an GUI NOT SUPPORTED sy-subrc error. It seems this does not work for the NWBC view. Does anyone have any idea on this?

Thanks in advance

Shuvodeep