Lol, I was just wondering. I'll be loaded on caffeine that day, so I was wondering if I have to pee will i have to wait the end of the block, or can i just go in the middle of it.
If you really had to, sure. Taking a break in the middle of the block gets flagged as abnormal behavior and is subjected to whatever guidelines the NBME has in place for dealing with those for the USMLE test.
So... really, it's just better to wait until the end of the block.
Bring diapers.