The Outlaw 990 entry in the Harmony One's database is quite good. If you select Devices->AV Receiver, you will see screen buttons for all the 990's inputs. They have the default names, but you can change these to match anything you've customized on the 990.
It would be a little unusual to use these on a regular basis with the Harmony One because switching inputs is usually associated with selecting a different "Activity". The only time I do this is when switching between analog and digital inputs from my DVD player. I was doing this often enough that I added 2 custom buttons to the "Listen to CD" activity so I wouldn't have to bounce out to the AV Receiver device menu.
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Outlaw 990/7500
Cambridge Azur 840C
Oppo DV-981HD
Fronts: Ohm SFRS-11.200S3
Surrounds: Ohm Micro-Walsh short omni
Subs: Hsu ULS-15
Motorola/Comcast DCT6412 III
Panasonic PT-50DL54