drawer question

[Mark Swindell]

I want a drawer stack to appear to the right of my main stack, IGI.

Main Stack = IGI
Substack = Guess
Substack = AnimalList

Script of button on substack "Guess" reads:

on mouseUp
   drawer stack "Animallist" at right of stack "IGI"
end mouseUp

But:
The drawer stack only slides out of the substack "Guess," not the  
main stack "IGI" (and on the left, I might add).

What is wrong with my command?

Thanks,
Mark
OS X 10.4
Rev 2.8.1