ease out and stop random rotation expression

hello everyone,

i'm trying to work out the following problem:

i've got a composition with about 200 layers (each one contains a letter of the alphabeth); what i wanna do is to make them twirl around in a random rotation then gradually slowing down and stopping, forming the shape of a logo.

I managed to find this expression which satisfies my wishes:

segMin = .3; //minimum segment duration
segMax = .7; //maximum segment duration
minVal = -720;
maxVal = 720;

end = 0;
j = 0;
while ( time >= end){
j += 1;
seedRandom(j,true);
start = end;
end += random(segMin,segMax);
}
endVal = random(minVal,maxVal);
seedRandom(j-1,true);
dummy=random(); //this is a throw-away value
startVal = random(minVal,maxVal);
ease(time,start,end,startVal,endVal)

and i am able to stop/start it with another simple one, but i don't want it to stop so abrupt.
I'm trying to use a slider control to ease the stopping, but can't figure out which value to link it with.

I'm fairly new to animation with expressions and would be very thankful for any help.

regards bof