This was the position after 24. b6:
The game continued: 24... hxg2+ 25. Kxg2 axb6 26. axb6 gxh2+ 27. Kh1 (27. Kxf2 would have held on a little longer) Qg1+! 28. Nxg1 hxg1Q#
As Mark points out, his 25... axb6 was unnecessary. But it was a pleasing finish nevertheless.
You can play through the full game here: