Hi,
I had done a school project to control WMP in LabVIEW few years ago. I also used ActiveX to control the player. The most difficult thing was to find the suitable properties and mothods in the program. I needed to try many time and found documents from Microsoft. About your program, I think you should open the automation reference once only and do the rest then close it. Try to find in Microsoft website that how to use those properties or take a look of their newsgroup.
Bill