ok jan i have tons of ideas.

Firstly, I know its sticky and icky, but throw a peice of fly paper up somewhere. It worked for me, just make sure its not somewheres where it can stick to everyone and everything, and if you have cats, put it up high. I had a very funny but annoying accident when the kitten got it wrapped around him. Try getting that stuff out of fur. I tell you its difficult.

Secondly, get a small saucer. Put in the saucer a bit of dish soap, water, and a bit of sugar. Cover with plastic wrap, and poke a few holes in the top. In go the flies, to eat the sugar, where the glycerin in the soap traps them and doesnt let them fly out.

If that doesnt work, a tiny slice of some kind of fruit under the saran wrap the same way should.

If that doesnt work, i suggest making friends with the flies?