restricting column to latest date

HI all

I'm very new to Crystal reports and have a problem with a report I've been asked to look at that was built by another person that is sadly no longer with the company

I have a list of Clients and Client activity dates (and a few other things but the Client activity date is the thing I'm interested in )

Client | Client activity date |

Some of the dates could be in the future i.e next week next month i'm sure you get the jist

Some Clients have a number of activity dates associated with them, how can I restrict this to just one activity that being the latest date regardless of whether it is in the future, current or in the past?

Thank you