A Fractional Jet's autopilot was inadvertently disconnected by the First Officer using the EFB in his lap at FL340. Heading and altitude changes were made but only the heading change was questioned by ATC.

Narrative

During cruising flight; I became preoccupied with evaluating our fuel status because of stronger than forecast adverse winds aloft. I was updating the fuel flow numbers on the FMS keyboard while the First Officer (pilot not flying) was working with the tablet computer (EFB) resting on his yoke. When I looked up at the flight instruments; I noted a 20-25 degree bank; 3-4 degree nose down pitch and a 250 FT altitude loss. The autopilot was disconnected. I immediately initiated aggressive roll and pitch inputs to recover heading and altitude. After I recovered heading and altitude; the First Officer re-engaged the autopilot on my call. The flight continued to an uneventful landing at our planned destination. ATC did not communicate any concern about our altitude excursion but did inquire about the heading change. Discussion with the First Officer led to the conclusion that he inadvertently activated the pitch trim; which causes the autopilot to disconnect without an aural annunciation. The momentary trim activation was not long enough to activate the audible trim-in-motion annunciator. I should have transferred aircraft control to the First Officer and done the EFB and FMS activities while allowing him to monitor the flight instruments. The inadvertent pitch trim activation and resulting autopilot disconnect might have occurred anyway; but it certainly would have been noticed and corrected more quickly if I had not allowed my fuel concern to override procedural discipline.