How to read package tracking number TRACKN from table VTRKH in userexit?

Hi experts

    I want to get the package tracking number in user exit MV50AFz1.

    I don't see this updated in table VTRKH in the user exit.

    I could not find any work area for VTRKH.

    Is there some other work area in the user exit that will have this?

Thanks

Gopal