When it is launched
The event occurs when a user command is called, provided that a corresponding item is added to the main menu or the toolbar. User command identifiers have the formCI_UserCommand + <non-negative integer>.
Parameters
To add a user command to the main menu or the toolbar, use the
AppendItem or InsertItem and AppendButton or InsertButton methods of the IMenu and IToolbar interfaces respectively. Use the command identifier CI_UserCommand or CI_UserCommand + <non-negative integer>.
The following sample code adds a menu item for a user command with the command identifier CI_UserCommand + 1.
