Ok, SOOOO been there, done that, wrote the book!!!
It's AWFUL, isn't it??!!!
So, at the mall or anywhere out and about - try giving him your keys, your purse to look through, anything that he normally isn't allowed to have.
What we did with ds, and this sounds alot worse than it is (try it!) is to sit on the floor, with your legs spread open. Lay ds in between your legs wiht his head at your feet. GENTLY use your feet to hold his head in place (those darn squirmy bodies!!:)) while you use your thighs to hold body/legs in place.
And get the diaper change over as quickly as possible!!! :-)
I also always said somethign like "I'm sorry you don't like this, but it has to be done. Diaper changes are non-negotiable" (not that he understood the last part, but it always seemed to calm me down - those kicks can make you mad!!)
It IS a phase. And it DOES suck.
I now ask ds to come and lay down for his diaper change, and he does!!!!!
NEVER would have thought that would have happened!!!