[Elecraft] K3 together with P3 and EXPERT 1k possible?

[DL2FI. Peter]

Good morning all
I have seen some postings of EXPERT 1k users here on the reflector, I need
your help.

A friend has a K3 and a P3. Now he wants to connect his EXPERT PA to this
combo. The problem: The K3 RS232 is occupied by the cable to P3, both P3
RS232 are occupied by Cables to k3 and PC. Because he wants to use the
Expert with different Antennas on different bands, he wants the K3 to tell
the EXPERT on which band it should work. But how? I personally have a
K3/P3/KPA500, so I can´t try to find a solution. 

Thanks in advance

Peter, DL2FI