Wiring an unpowered mic through a pot

I had a mountain of spare computer parts around, so I decided to turn them into a touchscreen jukebox project. As the project progresses, I've been adding more and more ideas to the mix. The latest is a "karaoke mode". As a musician, I also happened to have had a microphone hanging around too. Brilliant!

So, I ran to rat shack, bought an XLR connector, and wired everything up. The mic is going directly to the sound system on the jukebox, which is just a 5.1 card and a butchered 5.1 creative surround system. The mic is going directly to the line in on the card. Everything works fine. HOWEVER, I want to ad an external volume pot, instead of trying to adjust the volume with software, as some people sing louder than others. I got a pot, and wired it up, and it made no difference in the volume. I'm not super experienced with potentiometers, so I assume that it's not doing anything because it has to be powered? Or is there a way to make this work without amping the mic circuit?

Thanks. Forgive me if this is in the wrong forum. 😎

-Jay