There are several reasons to not want to use a grain mill. They are large, they make a lot of noise, they are expensive, and if you only want a small amount of flour they are a lot of trouble to get out and set up. If you only want a few cups of whole grain flour there is a better way.
First of all the fresher your flour the better your baked product is going to be. And, if you are making bread using rye, it should always be very fresh. As soon as rye is ground it starts to turn bitter.
The solution, a burr grinder. Yes! a coffee grinder but one that can hold more then a cup of flour and a choice of grinds. Use it only for grain and be careful. Burrs are metal and can over heat and warp. I grind about 1 cup of grain and then let it cool before grinding a second cup. You can get one for as little as $30 up to $100. This $37 one at Amazon would work just fine.
I hope this encourages some people to try whole grains. You can store grain for years as long as it is dry and with a burr grinder you can have fresh flour anytime.
If you have questions please ask.