Try using Jerry Fairley's PERL script T2ext, which you can download from http://esd.lbl.gov/research/projects/tough/licensing/free.html.
This may not take you all the way to Tecplot, but some distance.
Thanks for the fast reply..Yes I'm working on it. Problem is that embarrassingly I don't know anything about perl. I guess that I've to build with the script a windows executable. Am I right? Afterwards I could try using EXT. I hope this is the right way.
Best regards from Germany