Auto-increment field based off specific entity values

[joy11]

What I'd like to try to do is set up an auto increment field in the accounts entity that will generate a 6 digit number based on the values of other fields. I use the account section for several different account types and to keep track of different account statuses. I would need the auto increment to generate the number only if the account type is "XYZ" and the account status is "ABC". It would need to work for accounts currently in the CRM that have their status changed and for new accounts added with those requirements. Is there any information available on something similar? I know a long time ago, I went through and did the video tutorial for a "Contract" entity which used the auto increment, but my use is more complex.