Keeping Exponential Scale "live" with expressions

I think this should work for what you're trying to do. For two keyframes it should give the same result as if you applied AE's exonential scale. If there are more than two keyframes, it will apply the exponential scale between each adjacent pair of keyframes. Should work for multi-dimensional properties as well. I just took it out of the oven, so it may not be completely cooked. Let me know if you run into problems.

n = 0;
if (numKeys > 0){
  n = nearestKey(time).index;
    if (key(n).time > time){
      n--;
    }
}

if (n == 0 || n == numKeys){
  value
}else{
  d = 1
  try{
    value[1];
    d++;
    value[2];
    d++;
    value[3];
    d++;
  }catch (err){
  }
  t1 = key(n).time;
  t2 = key(n+1).time;
  if (d == 1){
    v1 = key(n).value;
    if (v1 == 0) v1 = .0001;
    v2 = key(n+1).value;
    if (v2 == 0) v2 = .0001;
    k = Math.log(v1/v2)/(t2-t1);
    v1/Math.exp((time-t1)*k)
  }else{
    v = [];
    for(i = 0; i < d; i++){
      v1 = key(n).value;
      if (v1 == 0) v1 = .0001;
      v2 = key(n+1).value;
      if (v2 == 0) v2 = .0001;
      k = Math.log(v1/v2)/(t2-t1);
      v = v1/Math.exp((time-t1)*k)
    }
    v
  }
}

Dan