the way I explain Pot Limit to anyone is if you announce "raise pot" you put your call in, which is part of the pot and then match the pot amount
For example Post Flop (400 post flop) 3 players A bets 100, B calls, C announces raise pot, so calls 100 and then raises a further 700
Hope that helps Nick. It's weird sometimes as when I am playing pot limit I do get confused but if I am standing over the table I know exactly what the pot is and how much the maximum is.
Stu