Update Columns based on External Text file

[iMacFlats]

Hello....

I have a Spreadsheet with some 500 lines of data in it.

Let's say in COLUMN C I have an IP address... I have an external file, one IP address per line. I'd like to find a script that will look at the IP address in the external file, and if it finds a match, a given IP address in COLUMN C matches an IP address in the external file, UPDATE COLUMN A with "Yes".

Then, if possible, it would update COLUMN A with a "NO" if not IP matches.

Im new to Excel spripting. Thanks for any help.

This is on Windows (despite my screen-name).

[iMacFlats]

If it's easier, I can copy the list in the external file and put it into a different tab in the spreadsheet.