No, there isnt. You could go into services and stop it when you need too, just make sure to restart it.
I have found tho, thru multipule benchmarks(3dmark01+03,P95,Aquamark3d and CPU Hot Tester) that F@H really doesnt affect it. I have run each with and without F@H and there is very little difference. Nothing that I would EVER notice in real world situations.
There are 'batch files' you can use to sort of pause it, and I am sure someone will be by soon to show you them.
EDIT: See, he even beat me to it.