Any other tool would be better.
But I did finally track down the solution from the links... buried in there somewhere.
\nFOR %%F in (*.dis) DO ECHO %%~nF.dat\n
Now maybe I can spend another 10 years not having to work with this abomination.
You'd think that the richest guy on the planet would go back and fix DOS, since that's how he stumbled into his fortune. But as near as I can tell, he's ashamed of his roots.