I have a sliding glass back door. It has a fancy white window covering. The covering is a bunch of hanging slats that work together with a pulley system. When I pull one cord the slats all bunch together and open. When I pull the other cord, the slats rotate to keep light out or let light in. My problem is the cords have become disengaged from the slats. I have to do everything by hand now. I don't know what I have to do to line up the cords on the pulley. Is this a repair job I can do myself, or should I call someone. Who should I call? How much should it cost? I keep thinking I can put a screw driver to the unit and open it up and figure out how to line everything up, but I'm afraid I'll break it. Any ideas?