To handle Excel files, the easiest way is to use an API like JXL (->google).
Then you can iterate through the cells of the first row until you get the cell-content "email" (the header of the column your looking for).
Now you know what column number your email adresses are stored in and you can iterate through the cells of that column and read
out all the email-adresses.
You could do it without an external library if you convert the Excelfile to a CSV first, and then read the file with a Scanner or whatever you