problem starting crusade

I want to start a crusade but don't want to declare war on the Egyptians. However, I am at war with tthe HRE who are excommunicated, and I want to send a crusade there to pick p some crusader mercenaries to send back to London.

But the Pope says its too soon since the last crusade. How long till I get to start up??

I think it is about 20 turns until you can call another crusade

10-13 turns 90% of the time. After the last one finished.