Compile/Compare Repeating Lists and Mark Missed Items

Hello,
I have a spreadsheet that generates two separate sheets of data, we'll consider them a Scan in/Scan out system. My hope is to devise a macro that will grab the entries from both sheets as they are generated and compile their scan in and scan out. As we look at the attached spreadsheet, the ScanIn sheet is missing a scan for K1954, so the compilation marks it as missing. The ScanOut sheet is missing a scan for K2013, so it marks that as missing. This data will be coming in live, so we'll get the scan in and a few minutes later we'll get the scan out. It's okay if, during this time, it says the scan out is missing, but we could possibly have it fill this in after a set time when it can assume it's missing, let's say 30 minutes if we take this route. Take note, the Barcode items can repeat and change order, so it would need to recognize and compile with the most recent scan in if the latest scan out is missing. This project is still in its infancy, so I appreciate any help you can provide to making it a success! I'm happy to answer questions, and very appreciative of any time you put into this!