>Yes I did get both AddToMenu and RemoveFromMenu to work. However, I'm now working with Set Mark of... I'd like the active form instance to be marked but can't get this to work properly. I'm trying to set the menu's mark from the form's activate() but this results in 'no such menu or menu item is defined' even though the item is definitely on the menu. Any ideas?

Try something like:-

Local lnTot, lnBar, lcCaption

lcCaption = ThisForm.Caption
lnTot = 0
lnTot = cntbar("Window")
for lnBar = lnTot to 1 step -1
  if prmbar("Window", getbar("Window", lnBar)) = lcCaption
    Set Mark of bar lnBar of Window to .T.
    exit
  endif
endfor

Then the same in the deactivate to untick it.

HTH