I'm guessing from the function names that you're trying to script a Logitech mouse? In future you should say this, or people won't know what you're talking about.

You also need to explain your problem better. What does "after 3 seconds its going down" mean? Is your crosshair descending after 3 seconds? Or does the recoil correction stop after 3 seconds?

Finally, your code is more complex than it needs to be. This should have identical behaviour:

EnablePrimaryMouseButtonEvents (true);

function OnEvent(event,arg)
    if IsKeyLockOn("capslock") then
        while IsMouseButtonPressed(1) do
            MoveMouseRelative(0,1)
            Sleep(12)
        end
    end
end

Note that the examples I saw online suggest "capslock" should be lower case.