I think I understand what you are after, but let me see if I get this right - You setup netflow on the 6509 (we have 8 of them) to export traffic to Orion. I also must assume you have setup the switch as a monitored node as well?
Are you worried ports are getting changed or something? If you setup the 6509 to use the Orion as a syslog server, you can create rules to alert you when the vlan changes, as that is a syslog message that can be watched for.
Or - are you just wanting to see how much traffic is passing through a specific interface on a specific vlan?
I have not played with SNMP and the UDP's much, but I am quite sure you could create one to generate a tabel on the node view page to show what ports are in what vlan - perhaps a GET TABLE? Ill search to see if I can find one to use.