Can't seem to find what I'm looking for, and I'm not too savy at this
program, so what I'm trying to do is this...

I have 2 documents, one is a database of values (UPC codes) and the other
document is another list of codes. I'm trying to find out what codes are on
both documents (I actually need to know which ones aren't on the second
document). It's several thousand items, and so far, the only way I've been
able to do it is to highlight a value, copy and paste it into the 'find'
tool, and then toggle to the other document and hit search. It's taking
forever and it seems like there should be a much easier way to do this.
Thanks in advance for your help!