First of all: Thanks.
Your solution did exactely what i want, and i am fine with using a non-elegant version, if it works.
About that autoindexing + indexing the path:
I know this is stupid, and i changed it to not autoindexing. But these things happen, when you try to quickly expand an already existing vi and want to automatize with for loops instead of doing the same things over and over.
I am attaching the whole vi. it first was just the analysis, basically the inner loop, where i wanted to be able to vary the number and size of the parts of the waveform that go into the PSD to see how analysis time and numbers of averages effects the spectrum.
In the next step i created a vi that writes a string of two variables in a file, and then i wanted to do this for all files in a directory.
i am totally aware of the fact, that there are several dirty solutions. But i guess you are used to seeing these things, that could be done much more elegantely and efficiently, but if you try to get a quick solution that works for you and you learned Labview by trial and error, this is the way your vi´s look like.
By the way, what would you suggest to learn "clean" labVIEW programming ?
thanks again,
Philipp