I think that if your Projector has a RS232 input for commands and is compatible with the B&O system, there is also an RS232 connector on the BV7, which will carry the on/off signal. The only problem is that there are very few projectors with RS232 input (it's more commonly an output for the motorized screen), and those which have one are not always compatible with the B&O signals...
People which owns a BV7 32 should correct me, as I don't have one...