You can do this... if you're a dealer. Quick search on CL will yield of few of these "dealers" - I'm sure that's how OPs access to Manheim came about. I still have creds from the guy I talked to years ago, they fork over Manheim creds, you set your alerts, tell them to bid, and voila. Problem is, I never found one worth bidding on, and unless hyper local it's sight unseen (well the condition reports are getting much better). But yeah anyway, these guys are out there, and it's a pretty easy process.
Actually, you can log in yourselves and have at it! Don't place any bids (think you're locked out of that anyway).
Manheim - Member Login
Username: aagvip
Password: oveplus