Ranking Rows Based on Company Occurrences in a List

Hi, How do I rank rows based on one column? I have a List with several Contacts, some being from the same company. And I want to rank the column with the companies meaning: Company X (first time) = 1 Company Y (first time) = 1 Company X (second time) = 2 Company Z (first time) = 1 Company X (third time) = 3 .... Does someone have any experience on this and could help me out?