For those of you who are interessted in the topic. I solved the problem by myself.
in reply to Re^2: Check whether the file is in use by an other user
in thread Using Win32::OLE and Excel - Tips and Tricks
sysopen(FH, $file, O_WRONLY|O_EXCL) or die $!;
works fine for me and it even works if the file is opened via a shared folder.
Finally I want to apologize for my offtopic-postings. I thougt the "fileInUse"-check would be possible with a Win32::OLE-function and because of that I posted here and did not create a new thread. I hope I will do better in future.
Best regards from sunny Germany.