I attempted to change my front brakes (first time on my own) today on my 2006 Honda Civic. All seemed to be going well on the first tire (front driver's side) until I realized I didn't have a C-clamp or any other tool that could push the caliper piston back so I put the old brakes back in.
I hand twisted the bottom 12 mm screw back into the caliper pin just a little before using my socket wrench. But once I started to use the socket wrench, every twist also turned the caliper pin so it wasn't making it any tighter. Unfortunately, this also applied to turning it the other direction. I tried to loosen it but the pin just turned with the wrench that way too.

I hate for this to be the reason I abandon this myself and go to a mechanic. Any suggestions to get this loose? I tried to drive the car a little around my lot and the brakes work fine so this apparently isn't affecting it.
Below is just a picture I took during my set up. I tried gripping the caliper top with a wrench and turning the screw but the grip wasn't strong enough on the pin and just slid off easily.

 

Use a wrench to hold the caliper slide pin when you're loosening or tightening the flange bolt. It should not be hard to do.

 

just pick up some new slide pins, the way that thing looks it may be fairly corroded inside anyhow