Hi D.-
I want to say that this is a stage. 2 of 4 nephews did the same thing at the same age. At about 11 months, one stopped doing it, and the other one, well- he is almost 10 months and it is kind of hit and miss. We just used the changing table strap to keep them in place along with a hand, and our bodies pressed against the side of the table to keep them from rolling off. It's a ridiculous struggle, but I really believe they grow out of it.
I hope this helps
-E. M
P.S> There was some great advice from other mommies- a toy to distract them- a pacifier- anything. My sister hands her son the bottle of butt paste =), clean of course, and I hand him whatever, including a spare diaper. Anything that they normally want and can't get too that is baby safe and will distract for 30 or 45 seconds to get that diaper off and a new one on is perfect. =)