DeviceIoControl() and tape library

[djnewman]

Hi,
I'm attempting to manage a tape library in C# and need some information on using the various Win32 IOCTL_CHANGER functions. Microsoft has little help on the subject and referred me to the HP forums. I see one other posting about deviceiocontrol referring to getting the device open, but I am past that problem. Specifically, I would like to understand how to reference the library for tape load and eject. The IOCTL command in question is CHANGER_SET_POSITION. It takes 2 parameters consisting of structs of CHANGER_ELEMENT and I don't understand what values need to be passed in them.
Is there ANY documentation on how to use the command? I'll take it in any programming language, but it needs to be on the Win32 platform as it is very different from the UNIX one.
Thanks!
Dave