Tracing down data flow within an DB

Hello,

pls, many times I was wandering if there is an practical way of performing subject's issue. Namely,

1) if there is an App without source code, on production server and

2) corresponding DB, that is open i.e., it is possible to go through all the objects but, plethora of them

Question: upon CLICK event on the control located on the App interface, is there an practical way of how to follow data flow, entered on the interface controls, how to trace down which SP(s) have been fired out etc..etc...

DB itself is very, very complex.....

how to cope with such tasks?

thanks

bye