FAQ #2594, published on 2002-11-12
How can I find out by programming whether a scroll knob has been moved with the wheel of the mouse ?
Just add the code "Mouse Wheel" to your field. Testing the variable _EVE.wparam in this code will give you the direction of the wheel. The value of the variable _EVE.wparam is positive for an upward movement and negative for a downward movement.
See also : wd7, mouse, wheel, wparam, scroll