DN_MOUSECLICK

Dialog item ID or -1 if the user clicked outside the dialog.

Pointer to a MOUSE_EVENT_RECORD structure.

TRUE - the dialog callback function has handled the message, no further processing by the kernel is needed.
FALSE - continue processing the message by the kernel.

Control	Description
All	All dialog elements excluding hidden and disabled

1. For the DI_USERCONTROL control the mouse cursor coordinates are relative to the upper left corner of the control. For all other elements the coordinates are relative to the upper left corner of the screen.
2. The dialog callback function can handle the DOUBLE_CLICK event. For this you should check the MouseEvent.dwEventFlags==DOUBLE_CLICK flag:
3. If the user clicks outside the dialog, then:
   • the left mouse button is treated as if <Esc> was pressed;
   • the right mouse button is treated as if <Enter> was pressed;
   • other mouse buttons are ignored (for a multiple button mice).
   • If the dialog callback function doesn't handle the message with ID=-1, the dialog will be closed