Mapkey using right button menu

Hi all,

I'm not able to create a mapkey where I have to activate a command present in a right button menu, after selection a model.

Eg.

mapkey _test ~ Timer `UI Desktop` `UI Desktop` `popupMenuRMBTimerCB`;\

mapkey(continued) ~ Close `rmb_popup` `PopupMenu`;~ Command `user_popup_item_cmd`;

That command is not present in any other place on the ribbon.

Any possible solution?

Thanks