You should definitely be using two tables. Your check in table is related to your piece item table by the piece item key. Your check in table needs at least a foreign key field and a timestamp field.
You can create the check in record in a number of different ways. One is to find the record in a piece list table and have a button to create the new check in record. If the piece items are labeled with your key you can simply create a new check in record and add the piece item key to the check in record. This can be done even easier if your piece item is barcoded with its key.
I have actually figued it out using scripts and buttons!
Now does anyone know how to change the color of a button once it has been clicked? Using Filemaker 11