You'd need to disable Bluetooth on your Mac and reenable it as needed. 
Just turning off RB's Bluetooth Receiver will not be sufficient as the 
OS may still talk to the remote and allow it to attempt connecting to 
the Mac.

Depending on whether the BD Remote stores more than one pairing or 
not, this will be a solution or you'll have to go through the pairing 
process every time you want to use it with a different device. This is 
a hardware limitation then, though.

Regarding whether switching between paired target devices from the 
remote: no, this is not possible due to the way Bluetooth works. It's 
a hen-egg-problem: the remote decides itself to which device it wants 
to establish a connection. It is only after that connection has been 
successfully established that any button presses can be received from 
the remote.

Best regards, 
Felix Schwarz