I have routes like that, the way i did it was, put the flight number but with an extra number at the end to tell what leg number it is, like for example GAC30474 GAC3047 is the flight back to Hong Kong from Wellington NZ, 4 is the leg number, so it is GAC3047 leg 4 that way GACV pilots can fly say VHHH-YPDN which is GAC30461, and it will show up as that.
Cheers
Dan C