I'm looking for a way to verify if the current getwork I'm on is from the current, or last block. Would I be able to do that by looking at "prev_block", and checking against a stored array of the "prev_block" from the previous two blocks?

Like, I have an array with the two last known prev_block values in it. If the prev_block value from the getwork matches the newest stored prev_block value, I know it's from the current block. If it matches the oldest prev_block value, it's from the block prior to the current. Correct?