Heads up, I added one extra inPoint, so this expression can work anywhere on the timeline not just frame zero. Thanks again.
freq = 2;
amplitude = 350;
decay = 6;
easeTime = 0.7;
if (time >= inPoint){
val = amplitude*Math.sin(freq*time*2*Math.PI)/Math.exp(decay*(time-inPoint));
easeIn((time-inPoint),0,easeTime,0,val)
}
else{value}