Thanks!
Meanwile I did some digging into batch files, it sure is an ugly language, but this seems to do the trick. I post it here if anyone else is looking...
---
@ECHO OFF
echo Running awk on all PT1.trk files
for /f "delims=" %%i in ('dir /ad/s/b') do (
cd %%i
if exist PT1.trk (...