If your firm uses Excel for anything beyond casual notes, timekeeping, trust ledgers, matter budgets, billing exhibits, the hard part usually isn’t the math. It’s getting the output to look the way your firm always presents it. Currency in the right format. The trust reconciliation laid out the way your bookkeeper expects it. The naming convention a paralegal has used for years. None of that is difficult. It’s just repetitive, and someone ends up re-explaining it every time a new person touches the file.
Microsoft just fixed part of that, building on Copilot Memory. As of June 2026, Copilot in Excel can learn formatting preferences, naming conventions, and report styles once and apply them automatically after that. Tell it how a client billing summary should be laid out, and it remembers, instead of you correcting the same thing every month.
The part that matters more for a firm
The more useful piece for a firm is what Microsoft calls workbook rules. Instead of preferences living in one person’s Copilot settings, the rules live inside the spreadsheet itself, in a sheet called .Rules, and travel with the file when it’s shared. Point Copilot at a good example of how a trust reconciliation should look, define how a billing formula should calculate, or have it read an existing sheet and infer the pattern.
That solves a real problem in firms with more than a couple of timekeepers. One paralegal builds the monthly trust reconciliation one way, another builds it differently next month, and a partner reviewing six months of files is suddenly looking at six different formats for what’s supposed to be the same document. Workbook rules keep that consistent without a partner having to re-explain the standard to every new hire.
What still needs a person
Here’s where the duty of supervision comes back into the conversation. ABA Formal Opinion 512 makes clear that a lawyer stays responsible for output that came from an AI tool, and that includes anything Copilot touches in a trust ledger or a billing exhibit. Workbook rules can enforce a consistent format. They can’t certify that a trust account balances or that a billing total is correct. Every AI-touched figure still needs a human check before it goes in front of a client or a bar auditor, the same way it would if an associate had built the spreadsheet by hand.
Worth setting up this week
Personalization is already available to Copilot in Excel users on web, Mac, and Windows. Workbook rules are still rolling out to a subset of users, so your firm may not see the option yet. If your firm rebuilds the same trust reconciliation or billing report every month, this is worth setting up the moment it’s available. Our managed IT services for law firms help firms figure out where Copilot genuinely saves time and where it just adds a new step someone still has to check, particularly on anything touching a trust account. Reach out if you want a hand sorting one from the other.