SendInput and wheel movement

[Razoth]

Hi,

I've got a problem with simulating wheel-movement in the SendInput function.
I get my wheel to move forwards, but i have no idea on how to move it backwards.

from MSDN reference:

mouseData
Type: DWORD
If dwFlags contains MOUSEEVENTF_WHEEL, then mouseData specifies the amount of wheel movement. 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. One wheel click is defined as WHEEL_DELTA, which is 120.

so mouseData specifies the wheel movement, and negative values indicate a backward rotation. But it is from type DWORD, so it can only contain positive values?!

How do i simulate negative wheel movement?

pls help

edit1: btw. thats how my code looks right now. (with -1 < RY < 1 )

INPUT in;
in.type = INPUT_MOUSE;
in.mi.dwFlags = MOUSEEVENTF_WHEEL;
in.mi.mouseData = RY * 120;
in.mi.time = 0;
SendInput(1, &in, sizeof(in));

edit2: my code above is working (i accidentially exluded negative values of RY myself), but i still dont get why.