I want to be able to put a checkmark beside a menu item when the user selects
that item from the menu. For example, under the View menu when the user
selects Task Pane the pane appears and a checkmark appears beside the 'Task
Pane' on the menu.

I would expect something like CommandBarControl.checked but it's not that
straightforward.

I used to know how to do this but the method has slipped my mind. Please help.

Thank you.