YES, it's amazing what you can animate just by controlling the expressions of one or more parts, by linking them to the system parameter FrameNumber.
You need to create the system expressions :
FrameNumber=0 (note the capital letters)
If you make some mating conditions creating expressions (or any other feature etc. creating expressions) you can use the FrameNumber expression.
e.g. change a distance mating condition from 100 to 200 during 20 frames:
distance = 100 + (200-100)*Framenumber/20
Now, in Animation options, tick the "update expressions" field, and create an animation after defining some frames (just add one with 20 frames).
Erland R. Nielsen
Denmark