This macro maps a command message to a member function.
The command ID.
The name of the message-handler function to which the command is mapped.
It indicates which function will handle a command message from a command user-interface object such as a menu item or toolbar button.
When a command-target object receives a Windows WM_COMMAND message with the specified ID, ON_COMMAND will call the member function memberFxn to handle the message.
Use ON_COMMAND to map a single command to a member function. Use ON_COMMAND_RANGE to map a range of command ids to one member function. Only one message-map entry can match a given command id. That is, you can't map a command to more than one handler. For more information and examples, see Message Handling and Mapping Topics.