Excel 2007 : Using 'if' command and vLookup function

Hi all,

Although I have used Excel for years, I've never really had the reason to delve into it. However I now find myself having to change and manipulate large lists of data and know that excel is certainly up for the job, me.... well I don't know where to start.

If anyone can point me in the right direction it would be really appreciated.

Basically I have a sheet that has 9 columns and over 20,000 rows (sheet1). I need to make changes to some of the rows, roughly 500. The rows I need to change is contained in another sheet (sheet2), with 500 or so rows.

I first need to identify the row(s) that needs to be changed on sheet1 by matching the contents of one of the columns that appears in both sheets. Then the column next to it needs to be altered from 'Yes' to 'No'.

My problem is that I don't really know the functions within excel to search so don't know where to start. From what I have seen, I think I need the vlookup?

I have also taken the liberty of uploading a file if anyone can assist. It would be most appreciated


Thanks in advance,
Michael