Can you outline a situation where this would be useful or necessary?  (That’s not an attack, I’m genuinely curious.)

Never mind, I read Clucky’s Escrow and I see what you mean now.  But the last sentence doesn’t seem like it’s saying what you want it to.  Shouldn’t it be more along the lines of “Until that point, the original posting Corporation may take back the Products.  If at any time the post’s Expiration Criteria are met, the Escrow condition may no longer be triggered.”?

Hmm… maybe “Expiration Criteria” isn’t the best name, but that can be changed later.  I want Corporation X to be able to put Products in escrow, while making a binding promise that X won’t retract the offer before certain criteria are met.  As for why this would be useful….

Suppose I wanted to offer [corporation A] a reward if and only if [condition B] is true at time of [trigger C].  If I place the reward in escrow triggering on “B being true at time of C”, then I can’t be screwed, but I will probably not be trusted, since I can screw A by waiting for A to make B true, and then retracting the offer before C ever happens.  In order to make my offer trustworthy, I need to be able to assure A that the offer will not be retracted before C occurs.