I kind of agree with TangoAlphad but if you HAD to make an attempt in such circumstances you could use the technique mentioned by Sparky Immeson in his book Mountain Flying.
Find the halfway point on the runway and mark it with something, or note some feature you will be able to see on the roll. On takeoff if you get 70% of flying speed by that point you will get off. If not abandon and stop in the remaining half. This assumes the second half of the runway is much the same as the first half and takes no account of obstacle clearance.