Title: Detect a wheel of mouse
Use GetSystemMetrics function with SM_MOUSEWHEELPRESENT parameter.
Note: for Windows NT only.
procedure TForm1.Button1Click(Sender: TObject);
begin
if GetSystemMetrics(SM_MOUSEWHEELPRESENT)<>0 then
Label1.Caption:='You have a wheel'
else
Label1.Caption:='You have not a wheel';
end;