The framework calls this member function after each interval specified in the SetTimer member function used to install a timer.
afx_msg void OnTimer( UINT_PTR nIDEvent );
Specifies the identifier of the timer.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.
See the example in CWnd::SetTimer.