🚀 go-pugleaf

I'm porting a DOS program to Windows (using TP for Windows), and am having 
trouble getting it to be civilized.  It has some long loops where it 
occasionally writes to one window; the original never gives up control,
so in Windows everything else comes to a halt until it's done.

I'm trying to civilize it by putting occasional calls to Yield into the 
loop, but it's ignoring mouse events..  If other windows have
been invalidated, the Yield works, they get redrawn, and mouse actions
get processed.  However, if all other windows are idle, the Yield doesn't
seem to do anything, even if I've clicked the mouse outside the current
application.  

Is there some way to configure what sort of behaviour Yield has?  It's not
even mentioned in Petzold, and the TPW documentation is minimal.  I don't
have the SDK manual.

Duncan Murdoch