You have Triggers in FileMaker. You can set OnObjectModify for that specific field and have a script attached to that trigger with all kind of logic that you want to have.
on your second layout show a portal with th e10 records you are interested in, on the first table add a field called check me, then when you select it in the portal, it is already checked, no more logic needed
Thanks for your suggestions! What ended up being much simpler (from a creation and user interface standpoint) was creating a list view layout from the Book List table, then creating objects with scripts that froze the window, performed a find for the book name, and changed the Status field to Checked Out/In.
Thanks for your help!