I'd be inclined to sort the records by Customer ID, then Date (whatever the date field is that your refer to). The date should be sorted in ascending order.
You can then supress multiple records in the detail line by using the Previous() function.
eg. In the Suppress section of the detail section, put in
Previous(CustomerID) = CustomerID
This have the effect of only displaying the first record of each unique CustomerID and as it's sorted by Date as well, each one shown will have the minimum date.
I hope I've explained that OK and I hope it helps.