C.P.
Hello Candy,
Here is a link.
http://www.wikihow.com/Make-Natural-Outdoor-Fly-Repellent
I wonder if you plant mint and rosemary around the yard if that would keep them away.
For my cousin's wedding last summer I got little satches and put in cotton saturated w/ peppermint oil and hung them around the tent and outdoor areas. no problems /w flies or mosquitoes. =) but doing this every day would be too much.
Good luck! ~C.~