Counting instances of same record

Hi All,

I have a spreadsheet which has three columns:

Email Address, Zip Code, and Newsletter Code

It is a list of email recipients who open my organizations email newsletter and I am trying to see who opens the emails consistently.

I want to count how many times the same email addressappears. iue if [email protected] opened newsletters 01012009 and 02012009, there will be a row for each.....and I would like to create results that would say:

[email protected] : 2 instances

Not sure if this makes sense....but any help would be appreciated.

Thanks
g