Hi,
Sorry, but I don't believe that's possible. Even if you can identify the program, there could be multiple transactions that executed it.
The only possible way, I think, would be to add an enhancement / badi which uses the callstack to determine the calling transaction at the time he event is raised (and then stores it somewhere).
But that's not very elegant.
Why do you need to know the triggering transaction? To influence the workflow? If so, another approach might be this: pass the transaction code as an additional parameter to the workflow event & then pass that to the workflow.
cheers
Paul