The WM_MOUSEMOVE message is posted to a window when the cursor moves. If the mouse is not captured, the message is posted to the window that contains the cursor. Otherwise, the message is posted to the window that has captured the mouse.
A window receives this message through its WindowProc function.
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Parameters

wParam -- Indicates whether various virtual keys are down. This parameter can be one or more of the following values.
MK_CONTROL - The CTRL key is down.
MK_LBUTTON - The left mouse button is down.
MK_MBUTTON - The middle mouse button is down.
MK_RBUTTON - The right mouse button is down.
MK_SHIFT - The SHIFT key is down.
MK_XBUTTON1 - Windows 2000/XP: The first X button is down.
MK_XBUTTON2 - Windows 2000/XP: The second X button is down.

lParam -- The low-order word specifies the x-coordinate of the cursor. The coordinate is relative to the upper-left corner of the client area.
The high-order word specifies the y-coordinate of the cursor. The coordinate is relative to the upper-left corner of the client area.
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The WM_MOUSEWHEEL message is sent to the focus window when the mouse wheel is rotated. The DefWindowProc function propagates the message to the window's parent. There should be no internal forwarding of the message, since DefWindowProc propagates it up the parent chain until it finds a window that processes it.
A window receives this message through its WindowProc function.
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Parameters

wParam -- The high-order word indicates the distance the wheel is rotated, expressed in multiples or divisions of WHEEL_DELTA, which is 120. A positive value indicates that the wheel was rotated forward, away from the user; a negative value indicates that the wheel was rotated backward, toward the user.
The low-order word indicates whether various virtual keys are down. This parameter can be one or more of the following values.
MK_CONTROL - The CTRL key is down.
MK_LBUTTON - The left mouse button is down.
MK_MBUTTON - The middle mouse button is down.
MK_RBUTTON - The right mouse button is down.
MK_SHIFT - The SHIFT key is down.
MK_XBUTTON1 - Windows 2000/XP: The first X button is down.
MK_XBUTTON2 - Windows 2000/XP: The second X button is down.

lParam -- The low-order word specifies the x-coordinate of the pointer, relative to the upper-left corner of the screen. The high-order word specifies the y-coordinate of the pointer, relative to the upper-left corner of the screen
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