I'm guessing you mean how to do this while you're debugging?  You can try setting the form enabled and visible properties to .t.  Or just release them.  Are you not sure how to reference them?  Here's a quick and dirty way...

ni = 1
do while .t.
_screen.forms(ni).visible = .t.
_screen.forms(ni).enabled = .t.
ni = ni + 1
if type('_screen.forms(ni)')<>'O'
  exit
endif

...snip
>enabled=.F. But sometime, due to the programme error, all three forms are "disabled" and visible=.F. also. After that, I cannot close the formset and cannot modify the form unless quitting VFP. So, I would like to know if there is any other way except quittin gVFP. Thanks.