detect windows messages to bp window

You can, but it's kind of a hack. Send a WM_CHAR message with the character code in the unused unicode utf-16 range ($d800-$dfff I think). Then just detect event $103 in Blitz. You'll have a harder time getting your lparam and wparam data, though (if you need it at all).

This is akin to what BLESS does and it works pretty well.