SetCapture (Compact 2013)
This function sets the mouse or style capture to a specified window that belongs to the current thread. After you call this function for a window, the window captures mouse input that occurs while the mouse cursor remains within the window. The window also captures mouse input that occurs when the user presses a mouse button while the mouse cursor is located within the window and continues to hold the mouse button down while moving the mouse. Only one window at a time can capture the mouse or stylus.
HWND SetCapture( HWND hWnd );
[in] Handle to the window in the current thread that is to capture the mouse.
The handle of the window that had previously captured the mouse indicates success. NULL indicates that no window previously captured the mouse.
Only the foreground window can capture the mouse. When a background window attempts to do so, the window receives messages only for mouse events that occur when the cursor hot spot is within the visible portion of the window. Also, even if the foreground window has captured the mouse, the user can still click another window, bringing it to the foreground.
When the window no longer requires all mouse input, the thread that created the window should call the ReleaseCapture function to release the mouse.
This function cannot be used to capture mouse input meant for another process.