Enabled menu items can be selected; disabled menu items cannot.
If the Enabled property is set to true in the menu item's Property view, the menu item is active.
If you want a control to appear but be inactive, set the Enabled property to false. For example, a menu item might be active only after the user has selected a particular option. In this case, initially display the menu item as disabled, so that it appears dimmed. In the script for the menu item, enable the menu item when the user selects the appropriate option.
menuitem.Enabled=TRUE