I have an object spinning with starting rotation and a spin step i.e. how many degrees it moves each time interval. I want to decrease the spin step linearly over a given time period so that the object rests at a given angle.

I want to calculate the decay rate (for the spin step) for any given time and spin rate accross a delta angle?

Sorry if this is not very clear, Its a bit like spinning a wheel and wanting the wheel to spin for a fixed amount of time and come to rest at a fixed stop point.

Any ideas?