When you have an sacrifice and an fortress in your hand, you can trash the fortress due the "Advance" and go for the Grand markets.
This line makes me think you may be a little confused. When you buy the Advance event, you have a chance to trash an Action to gain an Action, and yes, this is particularly good with Fortress and Grand Market. But if you are trashing an Action for some reason other than buying Advance -- such as because you played Sacrifice -- then there is no additional effect caused by Advance. It isn't some sort of global "when you trash an Action" effect.
My apologies if I am misreading you and you totally understood this already!