velocityAtTime expression error

Hello, I'm trying to add a simple bounce expression to my animation

but i keep getting the same errors, either this:

or this

the expression itself is as follows:

amp = 5.0; freq = 2.0; decay = 4.0;

n = 0;

if (numKeys > 0) {

  n = nearestKey(time).index;

  if (key(n).time > time) { n--; }

}

if (n == 0) { t = 0; }

else { t = time - key(n).time; }

if (n > 0 && t < 1) {

  v = velocityAtTime(key(n).time - thisComp.frameDuration/10);

  value + v*(amp/100)*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);

}

else { value; }