Question about updating records

Question about updating records

I am creating a Mileage Tracker for my motorcycle group. I would like for the application to update existing records when a user submits new data. Let's say I have 3 fields:

Name
Email
Mileage

If User1 inputs 350 miles one day, then comes back next week and inputs 225 miles, I want to have the app check to see that User1 already exists as a name, so add the new mileage data to the current record, instead of making a new record. To keep a running total of mileage per user. Does that make sense?

I am sorry if this is a simple question, for some reason I just cannot find any documentation on it. Thanks!