Compare Columns and Find Difference

Hi I am fairly new to excel and trying to figure out something and any help would be appreciated. I scan out parts to techs everyday and then scan them back in the next and need to figure out what hasn't came back. Each tech has his own workpage in the workbook. Column A1:A150 would be scanned out parts and B1:B150 would be scanned in parts. I need to compare Column B to Column A and remove the number from A if its on B, or something to that effect so we can quickly see what parts were not returned.
I will attach an example of one of the sheets from the book. Thank you in advance for your help. I'm sorry but it won't let me upload the page because its a .rar file and I don't have winzip on the company computer. Still any advise would be appreciated.