IF THAT IS THE ONLY FUNCTION YOU WANT THE CIRCUIT TO PERFORM then you only need a common bus which would be connected to both inputs and outputs. If it was connected like that then :
MOV R1,R2 Enable R1 out, enable R2 in, pulse the clock line.
MOV R1,R3 Enable R1 out, enable R3 in, pulse the clock line.
MOV R2,R3 Enable R2 out, enable R3 in, pulse the clock line.
MOV R2,R1 Enable R2 out, enable R1 in, pulse the clock line.
MOV R3,R1 Enable R3 out, enable R1 in, pulse the clock line.
MOV R3,R2 Enable R3 out, enable R2 in, pulse the clock line.
Another way you could connect it would be to have a tri state buffer between the output and input bus's in your circuit in post #11 and enable it's outputs when you wanted to move data.
Les.