Navigation issues - actionscript help needed

okay, it seems that i am too stupid to solve this simple problem, but i bet you guys can help me out. basically - cause i cant talk too much about the project and i cant actually post the .fla right now - i want to achive the following:

a. i am in _root.main.sitemap right now in the first frame, wherein i want to select where to go in the website / flashmovie.

b. when i click one of the buttons there, i want to go to _root.main.agentur(“mehrwert”), which is not the first frame in this clip, and _root.main.sitemap and _root.main.agentur are NOT placed in the same frame of _root.main

so when i try to use _root.main.gotoAndPlay(“agentur”) everything works out fine, cause i labeled the frame, where the agentur-clip is placed, “agentur”. but after i am in _root.main.agentur the buttonscript stops and i dont know how to get the the “mehrwert” label in this clip.
it might sound a little bit confusing, but i hope i made myself clear.

any help, hints, tips would be highly appreciated - thx cyze.