The menu resource that you define for your extension's menu must use menu-item identifiers in the range 1 through 99. When the user selects an item, the extension receives a command notification, which is the actual identifier of the selected item as defined in the resource-definition file (which has the .RC filename extension). The command notification is not the sum of the delta value and the identifier. An extension DLL's FMExtensionProc function carries out commands by processing command notifications.