Open the device from within the coinstaller. How?

Hello, group.
I have a driver with a coinstaller (this is a USB device driver which
enumerates as a COM-port)

I see my device in the device manager's list of COM-ports (like COM8)
and see my coinstaller's property page there, which works if I manually
specify
in this page that the port is COM8 (then I do CreateFile ("COM8") ...)

I believe that this is not the best way to open the device instance and
that
somewhere in the DeviceInfoSet/DeviceInfoData parameters of the
coinstallers' callback there might be information good for opening
exactly the current device instance thus avoiding "manual enumeration"
through
COM-port number.
I believe, but cannot guess where. :-)

So, could somebody suggest how to open the device from within
coinstaller property page's callback?
(i.e. how to find from there a device name good for CreateFile to open
it)

Thank you.