Successive crossings of the same passage

Hi, all !

I must keep track of the number of times the player has crossed a given passage, and trigger an event at a certain point. How can I do that? Increment a variable at every crossing? It seems that, when the passage loops on itself (a way to simulate a classic "for" loop) the variable is reset at every turn (it is first set in a "header" passage).

Thanks in advance.