Hi Bob,
The answer is no, that is not possible.
The reason is that, due to a strange design situation within the Raspberry Pi circuitry (and not the B2), if you wish to record through 'Aux-In', the B2 has to 'disconnect' the internal HDD (and also the CD) from itself, and then switch its 'source' to (micro)SD card. The B2 then records the 'Aux-In' music/ data tracks to the (micro)SD card. The 'Aux-In' input can be heard on the output channels.
When you have completed your recording, you switch 'Aux-In' off and the B2 will reboot itself again, and will reconnect the internal HDD and CD. To move the recording from the (micro)SD card you go into 'Settings' --> 'Get Recordings' and this function will copy the recording to the HDD, under artist name 'Unknown', album name 'Unknown'.
Care needs to be exercised here, because if you can can only do one recording at a time, as each successive recording will overwrite the previous one.
Regards,
Peter.