[alexey_ma]

Из MSDN к WM_MOUSEWHEEL :

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Syntax

WM_MOUSEWHEEL

    WPARAM wParam
    LPARAM lParam
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Remarks

Use the following code to get the information in the wParam parameter: 

fwKeys = GET_KEYSTATE_WPARAM(wParam);
zDelta = GET_WHEEL_DELTA_WPARAM(wParam);

Use the following code to obtain the horizontal and vertical position:

xPos = GET_X_LPARAM(lParam); 
yPos = GET_Y_LPARAM(lParam); 

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