Hi, Doug
Try using _SCREEN object:

LOCAL lFormExists
lFormExists=.f.
FOR i=1 to _SCREEN.FormCount
IF _SCREEN.Forms[i].Name='_Your_Form_Name_'
_SCREEN.Forms[i].ZOrder(0)
lFormExists=.t.
EXIT
ENDIF
ENDFOR
IF ! lFormExists
DO FORM _Your_Form_Name_
ENDIF

BTW, instead of "_SCREEN.Forms[i].Name='_Your_Form_Name_'" you
can use "_SCREEN.Forms[i].Caption='_Your_Form_Caption_'" or any
other property of form.

All the best.