Yim,

> I want to check whether an object exist or not in the form.
> How to do that ? Use what command statement ?

You can use

pemstatus()

if  Pemstatus(ThisForm, "txtMyText", 5)
   DoMyStuff()
else
   ??chr(7)
   wait window "MyText is missing"
endif

aMembers()

lnMembers = aMembers(laX, Thisform, 2)
acti screen
for each lcObject in laX
   ? lcObject
endfor

The form's objects collection

acti screen
for each loObject in ThisForm.Objects
    ? loObject.Name
endfor

To see if an Object really IS an object (and not just a null-Value) You can

if vartype(thisForm.txtMyText) = "O" and ! isNull(thisForm.MyText)
   ? "Valid Object"
endif

HTH