You cant do this yet… As NoiseRiser says: it still need implementations… But its one of the features that has been requested.
So far we have to settle with the BPM on the units, where we can move the beatgrid left / right or half/ double the BPM.
If you want to create a new BPM value, you need to do this manually in Engine Prime.
For now… But Denon has said that stuff regarding the BPM algorithm is right around the corner 