This message is used by the application to sub-class and change the behavior or appearance of the help window.
param1
USHORT controlres /* Res number of the control that was selected. */
USHORT usReserve /* Reserved value, should be 0. */
USHORT usevent /* The type of event which has occurred. */
param2
ULONG ulhwnd /* Window handle of relevant window. */