One idea:
If your forms have unique names, put this in the form.Load()

LOCAL lnCnt
lnCnt =0
FOR ji = 1 TO _Screen.FormCount
   IF _Screen.Forms(ji).Name==this.Name
      lnCnt=lnCnt+1
   ENDIF
ENDFOR
RETURN lnCnt<=1

>Hi,
>
>How i prevent multiple instances of a form.
>I've already tried with WEXIST, but it doens't work correctly.
>
>Thanks in advance.
>
>Ricardo