Do what I did, find a CB that locks war leader.
As Prussian Emperor I needed to knock Austria down a peg (we had been allies 150 years, had great relations, but they broke alliance and went hostile to me. So now they need to get kicked around some, also they have 4 electors voting for them... need to fix that). Thing is they allied a ton of people. Silesia, Bosnia, Anhalt, etc (yawn), and Russia (yikes). With only Hungary and my vassals Austria is no problem, with Russia ready to sweep down my Baltic provinces? Forget that.
So I picked a CB that does double duty. Revoke Elector on Silesia. It locks leader, calls in only Austria, Bosnia, and Mantua, and lets me remove one of Austria's backers and replace with my own.
So find a CB that does the same, it really is the best solution if you want to wage a war that excludes Russia.