//segDur - This variable controls how often the playhead will be changed.
segDur = .5;// duration of each "segment" of random time
minVal = inPoint;
maxVal = outPoint - segDur;
seed = Math.floor(time/segDur);
segStart = seed*segDur;
seedRandom(seed,true);
startVal =  random(minVal,maxVal);
endVal = startVal + segDur;
linear(time,segStart,segStart + segDur, startVal, endVal);