updating data in a field consisting of existing data without deleting existing data.

HI techfilmguy! And i am a MS Access Trainer for 10 years and it would be great to send some screenshot of your table structure, e.g. a screenshot of your entity relationship model, if there is one so far.

Your first and second appointment about service statutes (detail table) and different vehicles (another detail table) should come together in one new table (master table) like "Service appointment" or something like that.

Why?

You need to settle a structure between tables and their fields FIRST. Then you can relate records from one table to another. I suggest, you should always create queries from the important fields and one of these queries is a data source for your form at third step.

You can see your relationships done so far with your Tab "database tools" - button for relationships. See attached screenshot for this.