Re: accumulation

Ok. I have 3 keyframes with a loop expression . The value goes from 0(key1) to 100(key2) and it holds till the third keyframe.
what i want is to add this value to position of the null. i mean, each time the loop is beginning it adds the value to the position value at that moment(valueAtTime).So finnaly i will have 0-100, hold, 100-200, hold...and so on.I know expressions don't have memory so that's why i think it's about accumulation.
I was playing with this expression but it is adding each frame value to the previous one so when i have the hold keyframe it will add 100 on each frame.

Hope this time i was more clear.
Thanks.

accum = 0;
f = Math.round(time/thisComp.frameDuration);
for (i = 0; i <= f; i++){
t = i*thisComp.frameDuration;
accum += slider efect.valueAtTime(t);
}