Thank you guys, it is what I was looking for.
I think with this VI and registry-key I am able to sovle the problem, thx.
To .txt:
You are right, it is possible to save the txt-file with tab-delimeter,
but the problem is, that the user has to choose that the file has to be opened with Excel (it is not so clear for some users).
Most of the users would dobble-click on a file to edit it. It is the reason, why I use the .csv file, by dobble-click on the file the excel starts automaticly.
Best regards: Alexander