speed control for ba6209

i want to make a speed control circuit for the ba6209....
i have a number wich is represented by 4 bits(or i can use a decoder to have 10 decoded outputs wich is the better solution) wich will be the speed. but how do i control the ba6209 so thet i have speeds from 10 or 20% to 100%
i was thinking of getting the outputs and contolling a duty cicle of an oscilator wich will drive the ic. also the ba6209 has a voltage control pin but i dont am not sure how to take the 10 decoded(or maybe less then 10) outputs and make a refernce voltage....
any ideas?

Use your decoded outputs to switch between any 1 of 10 different value potential dividers.