Reporting Services :: Grouping All Instances Of ESI Together

I have created a Table within SQL Server Report Builder, and the first field is a calculated field with the following code:

=Code.ChangeWord(Fields!NAME.Value)

Where the function is

Public Function ChangeWord(ByVal s As String) As String  
Dim strBuilder As New System.Text.StringBuilder(s) If s.Contains("ESI  ") Then     
strBuilder.Replace(s,"ESI")     
Return strBuilder.ToString()     
Else : Return s   End IfEnd Function

Now, when I execute this, it works beautifully ... except that the Grouping mechanism doesn't group all instances of "ESI" together, like I want it to.

How do I change this behavior so that it groups all instances of "ESI" together, like it should?