Using a barley mill for flour?

It sounds like you have a "grain crusher".

If it will crush raw (ie, not roasted) barley berries, it will likely crush raw wheat berries.

I have a similar device, which is a Chinese remake of a German "Shule" brand grain mill, but it does not make flour.

Another word used for processing wheat in a crusher is to "crack," as in making "cracked wheat".

I have sometimes used cracked wheat for breakfast cereal.  

You can also use  cracked wheat (soaked or partially cooked) as an add-in when making bread.  Or make a porridge from the  cracked wheat and include the porridge in bread. There are plenty of recipes out there for those.

When you crack wheat, it does give off a small portion of small particles called "fines."  These look like coarse flour. But if you sift them off, and re-run the rest of the cracked wheat through the cracker/crusher/mill, there is a limit to how much "fines" you get.  Well, it also depends on how close you can get the rollers.  In the end, you'll get some "fines" (coarse flour) and a bunch of larger sizes that you can't really call flour.  Even then, it would take several passes, especially if you have only a 2-roller setup instead of a 3-roller.  

Try it with some of your barley, or other whole grains, and see how fine you can get it.

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Becasue I'm cheap, I use my Chinese/Shule grain crusher as a preliminary step prior to running its output through a powerful Vitamix blender to make flour. (mini batches of 8 oz by weight at a time, 30 seconds blend time.)   This is because the blender's  plastic container gets scratched if your put in whole berries.  Plus it takes longer and heats up the flour if you try to blend whole berries into flour in one step.

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Net:  No, your grain crusher likely can't make flour. But it can make cracked wheat for breakfast porridge, bread add-ins, and prepare whole berries for the blender if you make flour that way.

Prosit!

Please be aware that beer is made from malted barley, not raw barley. Malted barley is a lot softer than raw barley and if your mill is designed specifically for malt, then raw barley or wheat might damage the rollers.

Lance