Simple Pot-Limit raising question

[The Setup]

I'm going to a casino for only the third time tonight to play in a pot-limit hold'em tournament and was wondering about something. This is a pre-flop raising question.

As far as I'm aware the minimum and maximum bet or raise pre-flop is between 2BB and 3.5BB assuming your on the button with only one caller in front is this correct?

However I start to get confused when there is a raise or a reraise in front of you.

Imagine the blinds are 50 and 100. If for example someone raises the pot to 250 and your next to act with a raising hand what is the mimimum and maximum you can raise the pot. I'd think that the minimum you could raise the pot to is 500 but I don't know what the maximum raise could be. [img]/images/graemlins/frown.gif[/img]

Also what about if there is a pot sized raise and reraise and you want to reraise again whats the min and max you can raise assuming the blinds are 50 and 100?

If there is an quick and easy way to calculate this I would really like to know.