No, the macro does not return a value it justs updates b0.
So you could use it like this:
SW1_SW2
If b0 = 1 then
code
elseif b0 = 2 then
code
endif
You could also include the code in the macro:
#MACRO SW1_SW2()
b0 = pinsC & $03
If b0 = 1 then
code
elseif b0 = 2 then
code
endif
#ENDMACRO
Then just one simple line does it all
SW1_SW2