How to use : vlax-put-property

Hello to all,

I have a mymenu.cui file. After (menucmd "p14=+mymenu.POP01") i can not see the menu in menu bar. May be the problem is that is set to false. That is the reaseon to start write next code:

(defun c:go ()
(vl-load-com)
(setq menu-list nil)
(setq acad (vlax-get-acad-object))
(setq mgs (vla-get-Menugroups acad))
(setq c (vla-get-count mgs))
 (setq n 0)
 (repeat c
   (setq menu (vlax-invoke-method mgs "Item" n))
   (setq menu-list (cons menu menu-list))
   (setq n (+ 1 n))
 )

(setq pops (vla-get-menus (nth 1 menu-list) ))
(setq pop (vlax-invoke-method pops "Item" 0))
(setq status (vlax-get-property pop 'OnMenuBar))
(vlax-property-available-p pop 'OnMenuBar)
(vlax-put-property pop 'OnMenuBar :vlax-true) ; <- Here I am receiving an error?
)

I can not set OnMenuBar on :Vlax-true.

Can any one help me?

Thanks!