'宣言
 
Public Shared Function GET_WHEEL_DELTA_WPARAM( _
   ByVal wParam As IntPtr _
) As Integer

public static int GET_WHEEL_DELTA_WPARAM( 
   IntPtr wParam
)

The return value is the high-order word representing the wheel-delta value. It indicates the distance that 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.