Unless you can create a dataset that joins the tables together from the two datasets you have now, you will have to use a LookupSet function to return each value from dataset2 that matches the CustomerID associated with the selected CenterID. Because LookupSet can only return one type of value at at time, you will need a separate LookupSet function for each customer value you want to return.

Assuming your tablix is built upon dataset1, the syntax would be something like =LookupSet(Fields!CustomerID.Value, Fields!CustomerID.Value, Fields!CustomerName.Value, "dataset2")

In a query, this would be a simple join between the two tables represented in each currently defined dataset, but if you cannot write your own query against the data, LookupSet may be your only option.