have not found a way to change bootorder directly, but there was a script which allows to enable or disable a certain boot device.
using this functionality i was able to force the vm to pxe boot by disabling booting off the hd and later reenabling hd boot during setup.
this way i was able to create my own setupprogram which creates a vm and starts a windows installation automatically.
attached is my modified script to change boot preferences.
