I'm new to excel but googled a lot today but was unable to find the answer. Hopefully someone can supply me with a formula/solution or can point me in the right direction. Its hard to explain so I start with a snippet of a (condensed) spreadsheet.

sheet 1
Author Book paragraph
author1 book3 1
author2 book2 3
author1 book2 10
author1 book3 4
author2 book2 1
author3 book3 10

Sheet 2
Author nr_of_books_published
author1 2
author2 1
author3 1

What I'm trying to accomplish is to calculate the number of uniqe books a certain author has published. In the example above for author1 this should be 2 and for author2 this is 1 and for author3 this is also 1. In sheet2 the input for the formula which calculates the 'nr of book publised' is colum1 (author), the formula is in colum2 where also the output is shown. The data is in sheet.

Wolverine2710