Macclesfield started brightly and might have scored in the seventh minute when Bullock picked out fellow new signing Allan Russell who slid a shot between Shane Higgs legs only to see it deflect past the post. But then Cheltenham took control with John Finnigan planting a header inches wide before Damian Spencer drilled a shot inches past the post.
They took the lead in the 18th minute when Kayode Odejayi picked out John Melligan who drove the ball into the roof of the net from the edge of the box. Cheltenham twice hit the woodwork in the second half with Grant McCann drilling a free kick against the underside of the bar before Melligan saw a firm drive crash off the outside of the angle.
Spencer then missed a clear-cut header glancing across goal from six yards. But Macclesfield were also unlucky with Paul Harsley seeing a half volley cleared off the line by Melligan and convincing appeal for a penalty after an apparent trip on Martin Bullock waved away by the referee.
Cheltenham looked to have sealed the game in the 81st minute when Melligan clipped a neat cross on to the forehead of Odejayi who nodded home from six yards.
Finally stung into action elegant midfield man Neil McKenzie drove forward bearing three men on a chinking run before lashing a low drive to the far corner just 30 seconds later.
Macclesfield then stormed forward with sub John Miles checking inside to pick out Bullock who fired home his debut goal from 15 yards.