Running lisp in one open dwg file that changes another open dwg file

[nick.seman]

I have two dwg files open "A" and "B".  I am running a lisp in "A"

Can anyone explain to me why in the following snip, the line gets drawn in "B" but the coordinate system gets set in "A" instead of "B"?

Thanks;

Nick

(vlax-for Doc (vla-get-Documents (vlax-get-acad-object))
   (if (= (vla-get-name Doc) "B.dwg")
      (progn
         (vla-activate Doc)
         (vlax-put-property (vlax-get-property zonesettings 'coordinatesystem) 'cscode "PA83-NF")
         (vla-AddLine
            (vla-get-ModelSpace Doc)
            (vlax-3d-point '(0 0 0))
            (vlax-3d-point '(5 5 0))

         );AddLine
      );progn
   );if
);vlax

[paullimapa · Accepted solution]

That’s because vlax-put-property function has no reference to doc but the vla-add line function does reference doc 

[LDShaw]

Following. 
I have not had much luck switching active documents. If there is a way to reliably do this I would like to understand it better. 
From my understanding AutoLISP does not always automatically switch the context to the new active document especially when modifying properties or adding objects it may still affect the initially active drawing, even after switching focus. 

[Sea-Haven]

This is very limited testing but seems to work.

; simple jump to another dwg that is open
; By AlanH Nov 2023

(defun c:dodwg ( / acdocs lst x ans but cnt)
(setq acDocs (vla-get-documents (vlax-get-acad-object)))
(setq cnt (vlax-get acdocs 'count))

(setq lst '())
(setq x 0)
(repeat cnt
  (setq lst (cons (vlax-get (vla-item acdocs x) 'name) lst))
  (setq x (1+ x))
)
(setq lst (reverse lst))

(If (< cnt 16)
  (progn
   (if (not AH:Butts)(load "Multi radio buttons.lsp"))
   (setq lst (cons "Please choose " lst))
   (setq ans (ah:butts 1 "V"  lst))
   (setq dbx (vla-item acdocs (- but 1)))
  )
  (alert "to many dwg's open will skip ")
)

(vla-addline (vla-get-modelspace dbx)
   (vlax-3D-point '(0.0 0.0))
   (vlax-3D-point '(30.0 50.0))
)

(vlax-release-object dbx)
(princ)
)
(c:dodwg)