Hi,
Have you tried using search... for RV60AFZZ and XVBRP? 
Because I found the answer in about 2 minutes, never having had implemented anything in this corner of SAP.
XVBRP is defined in interfaces of many function modules of function group V60A. The interfaces of those FM have been made global using the now obsolete feature for doing so.
You should be able to activate user exit despite syntax check complaining. However, XVBRP is available only during runtime of a function module whose interface includes it. If your user exit will somehow get triggered outside the context of such FM call, there will be runtime error (dump).
cheers
Janis