Hi Shawn
I think there are so many things you need to do.
1, Once you already created new tab in IW32, when click upload button, you need call function 'SAP_WAPI_CREATE_EVENT'. this function will ask you import Business object and event name.
2, Create a new BO and related attributes, method and event, which is used to above function.
3, Bounding your workflow with this new BO event.
For detail you need search it on SCN, so many threads here.
If i`m wrong, please correct me.
Regards,
Archer