You can use Set Menu Item Info with items from a runtime menu file. You don't need to insert items programmatically to use Set Menu Item Info. Use the Current VI's Menubar function to get the menubar refnum, then call Set Menu Item Info along with three inputs:
1. The menubar refnum.
2. The item tag for the item to be disabled or enabled. You may need to go back to the menu editor to get the tag, which may or may not be the same as the displayed item name.
3. A boolean wired to enabled.
I referred you to the examples just to see one part of the diagram.