BADI HELP!

hi to all, it already spent long time from my last post. This time I have some doubts on Menu Exits. I need to put an extra button on the menu bar of transaction va01 and vl01n. I already now how to use simple badis and filter badis.

Now my question is: does menu exit with badis allowed me to do this in a standard transaction like the ones i mentioned?

How to find that badis for any std transaction?

IF anyone has an example of any transaction please share with me, to understand the subject.

As usual, rewards points will be given for help. THANKS IN ADVANCE.