Report Designer Dynamic Filter

I have a requirement to add the ability to filter a report by partial last name, at the report level (i.e. not at the database server). In case someone else needs to work out how to do this, here is what I did.

Add a Parameter to the report. In my case it is named LastName, is non-queried, allows Null or Blank, and has a default of null.
Add a filter to the dataset that contains the field to be searched. Set its Expression to:
=IIF(Parameters!LastName.Value = System.DBNull.Value OR Parameters!LastName.Value = "",
Fields!LastName.Value, Nothing) ,
its operator to "="
and its value to =IIF(Parameters!LastName.Value = Nothing OR Parameters!LastName.Value = "", Nothing, Parameters!LastName.Value & "*")

voila!

Helen