How do I find and replace text in an excel file using text from a list box

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C#3.0

C#

I am needing help to find and replace text in an excel file. I would like to loop through a list box or a text file to accomplish this. The text will not always be the same. The reason for this is because I am getting usernames from an OU in active directory. Then I would like to search for each user name in the list box to see if it is in the excel spreadsheet. If it is, then replace it with an empty value. So the end result will be an empty cell. There will be multiple entries for each user name. I already have the code to get the usernames, just need help doing a find and replace in excel using c#. I have a winform setup with a button and 2 listboxes. The one on the left will display the usernames, and I would like the one on the right to display the end result. ie: deleted -or- not found.