Thanx for that clue

if ingroup(@wksta+'Administrators')
? 'Administrator '+@userid
else
? 'Not an Administrator '+@userid
? @serror
endif

I have enabled @serror and tried it gave me

Not an Administrator 000182
The specified domain did not exist.

if ingroup(@wksta+'\Administrators')
? 'Administrator '+@userid
else
? 'Not an Administrator '+@userid
? @serror
endif

Result was this…

Not an Administrator 000182
The operation completed successfully.

It seems it is not recognizing Local admin group.
_________________________
“I’ll not change you unless you don’t have intention to change yourself” --H:Quran