call existing RFC/BAPI from .NET server component

Hello all,

I would like to send information from an FI document to a .NET server component when some of the data changes on the SAP side. I have downloaded the SAP .NET connector and understand the examples using the RFC_CUSTOMER_GET test ABAP program. But I do not understand how to invoke server component mapped to an existing RFC/BAPI when a user changes the data via the SAP GUI.

Please point me in the right direction...

Thanks,