Distinct Count

I have a table Events which is a master detail with Attendees.

Attendees are connected to the contacts table and the account table.

I have a rollup summary that counts all attendees where the status is registered, however I  also need a distinct count of accounts.. We could have two spouses in one account. I need that to count as one..

Is there a formula that will make this possible

Event (master)

Attendee (detail) - has the status field

Contact (lookup field on the attendee)

Account (lookup field on the account) #Formulas #Declarative Lookup Rollup Summaries