I am trying to use the F bc= exclusion in advanced controls. My search uses multiple airlines with different fare classes required. how can I use the F bc = with multiple airlines

How would I enter the following in ITA Matrix

Origin LHR
Dest PER

Via IAH and SYD

Airlines

LHR to I AH - LH in bc W, V or Q
IAH to SYD - UA in bc W, V or Q
SYD to PER - QF in S, N or O

Thanks

Paul