KEB:
It's a guessing game untill we have an example of how Daron expects this function to be called.
.. I just took best guess.
With this type of functionality there are 2 issues.
Can you do it this way.
Do you want to.
That's Darons call.
Personally I would keep it simple and transparent.
The IAcadLayout has already been defined, so all that is needed is an in line call to :
;; return the translated Variant (two-element array of doubles)
(vlax-safearray->list (vlax-variant-value (vla-get-PlotOrigin AcadLayout)))
or
;; return an int, long, real, string, enumerator, boolean, Object etc
(vla-get-WhatEverProperty AcadLayout)