2000 323i Rear Drivers Side Window Problems

A few months ago I tried to roll down the rear drivers side window. It made a grinding sound and would not come back up.

At first I just held the "up window" button and had someone yank the window up. That works until they let go of the window and it tries to go back down again.

I found that if I press the "down window" button and have someone pull the window up and hold it it will stay up.

It still falls down a little when I'm driving (no more than about half an inch), and I have to just push the window back up.

I'm just wondering if someone could tell me what's wrong with it and possibly how much it would cost to get it fixed.

I'm also looking for cheap DIY fixes, since I really don't want to spend a lot of money on the ridiculously overpriced BMW parts. I have some little velcro thingys holding it up right now, and that seems to stop it from falling down even more (before I put those on there, I would sometimes fall a few inches down (wish is a pain in the ass to get back up alone).

Thanks for the help!