Approve Travel Request WF does not trigger.

Hi Experts.

I've been using WS20000050 for "Create Travel Request" option on TRIP tcode. But Now the final user needs to create "Expense Repor With Ref." Before the "Create Travel request" as i see, this option creates a request like a wizard, then in the travel pool it appeasr with the option "Create Travel Request", but, when the user saves the request does not trigger the WF. I try to modify the Standard, and add some "Triggering Events" like "Change Travel Req" and add some others like "Approve Travel request expense". But the same problem occur, no wf triggering. How can i check the correct event in this other way of create travel request?, or any experience?.

Thanks a lot for your help,

Steve.