Main menu bar popup menu

I made a new menu in the main menu bar with 2 items in it. Now that’s what I’d like to do with it:

The user can select only one of these two Items and the selected one shall get a checkmark. Furthermore I won’t to set one of the two by default if the user makes no selection.

How can I do that???

Use of a Global Property (App or Module) as Boolean (for the first MenuItem) and use it to Set or nset/Set (the other one) the Checkmark ?

Thank you for your Answer but I’m not sure what exactly to do. I’m really a newbie.
The new menu is only needed for window1. Is a global property still needed ore can I use the Variable related to Menu1? And how do I get the checkmark to the MenuItem?

Checkmarks (and other menu attributes) should be managed inside the ENABLEMENUITEMS event


Thanks a lot, now I got it!