[chuck-users] interpolated step? (equivalent to max's line)

Hi, I still feel new to chuck, and I'm wondering if there's a UGen that will make a (linear/whatever) ramp from its current value to a specified new value over a specified time? Might there be a way to hack the GenX or Envelope objects to behave this way? (For ppl familiar with max/msp, I'm looking for something equivalent to line~) I want to use this for modulation and for slewing controller input. Since the timescale i'm interested is on the scale of seconds/fractions of seconds, I suppose there's no real need to use a UGen rather than a class or function or something, but I'm still wrapping my head around the way that the ChucK language operates. Thanks, George