CRJ200 First Officer reports adjusting the aileron trim during the takeoff roll which immediately causes a 'Takeoff Config Aileron Trim' warning message. The Captain assumes control and rejects the takeoff.

Narrative

On the last leg of a 5-leg day the flight started normally. The Captain and I followed all checklists. We taxied to Runway 32L/T10 as assigned by ORD Ground. Approaching the runway (I believe we were number 3 or 4); the Captain called for the before takeoff check to the line. I performed my checklist flow and we read the checklist. Both of us visually verified that we had the green 'Takeoff Config O/K' message; and completed the Before Take-off checklist to the line. ORD Tower cleared us to line up and wait on Runway 32L/T10. We both verified the runway (the Captain verbally); ensured the runway was clear and taxied into position. While we were doing this; the Captain called for the Before Takeoff check below the line. I performed my flow and read the checklist. When in position; the Captain transferred controls to me and I accepted them; then we both verbally verified that the runway heading was correct. The Tower cleared us to takeoff on Runway 32L/T10 with a right turn to 040 heading (I believe). The wind was something like 270 at 9 (or possibly 280. I'm not sure of the speed; but I'm pretty sure it was below 14 KTS as we didn't have much wind at all that day). I added some left aileron to correct for the crosswind. I advanced the power to within 2% of takeoff N1 and called for the Captain to 'Set Thrust.' The Captain adjusted the thrust to the correct setting and said; 'Thrust Set.' We accelerated down the runway. I maintained the centerline and adjusted the wind correction as necessary. The Captain was scanning the instruments. At 80 KTS the Captain called; '80 KTS.' I verified the speed and said; 'Check.' At some point after that; but before we got to V1; I reached down and added some left aileron trim. Immediately; we received a 'Takeoff Config Aileron Trim' warning message (I believe that's the wording). The Captain called for the abort and took the controls. I gave him the controls and then called Tower to let them know that we aborted our takeoff. I had to call them three times because I kept stepping on other people. However; I did finally get through to them. They told us to exit the runway when able. They then canceled the takeoff clearance of the aircraft behind us; which I believe had not started its takeoff roll yet. We taxied clear of the runway onto Taxiway T between H and W and stopped to assess the situation. At that point; I told him that I had adjusted the aileron trim; and that it caused the warning message. The Captain notified Maintenance and verified that they needed to check out the airplane. I got a gate and called ground to return to a new gate. Ground again asked if we needed assistance; and I told them we did not. They asked; for their paperwork; the reason for the abort. I told them; 'We received an Aileron Trim warning message.' At the gate; the Captain wrote up the rejected takeoff. Maintenance arrived and the Captain explained the situation.