If I understand this correctly, you should really just be able to take the "Speed" value from Timewarp and multiply by the current time. Basically, how fast you are going times how long you are traveling.
spd = thisComp.layer("Timewarp").effect("Timewarp")("Speed")/100; spd * time
Edit: Just noticed that you said "Speed RAMP". That's a different mess all together. It might be possible, but this would be really complicated to accumulate the values while they change in value.
TL;DR: It's really hard.