Hide DetailsView Row if Null

I have a DetailsView control based off a sqldatasource with the following SELECT statement:

SELECT id
        , CASE title WHEN titlenew THEN NULL
            ELSE 'Title changed from ' + title + ' to ' + titlenew END AS title
        , CASE firstname WHEN firstnamenew THEN NULL
            ELSE 'First name changed from ' + firstname + ' to ' + firstnamenew END AS firstname
        , CASE middlename WHEN middlenamenew THEN NULL
            ELSE 'Middle name changed from ' + middlename + ' to ' + middlenamenew END AS middlename
FROM            tblAudit
WHERE        (varid = @varid)

varid is passed form a Textbox control. The query compares two fields of a given record within the table. If the fields are equal it returns NULL, if the fields are not, it returns the string showing the values from the 2 fields. An example result set might look like:

title                                                    firstname                                                          middlename
NULL                                                'First name changed from John to Roger'         NULL
'Title changed from Man to Woman  NULL                                                                 'Middle name changed from M to W'


I would like for my DetailsView (with Paging enabled) to only display the Rows which are not null. ie for the Result set above, Page 1:

First Name: First name changed from John to Roger

Page 2:

Title: Title changed from Man to Woman
Middle name: Middle name changed from M to W


I've tried multiple methods of evaluating the data of the Row and hiding it if NULL but the rows remain... ie

        protected void DetailsView1_DataBound(object sender, EventArgs e)
        {
            foreach (DetailsViewRow Row in DetailsView1.Rows)
            {
                if ((string.IsNullOrEmpty(Row.Cells[1].Text)))
                {
                    Row.Visible = false;
                }
            }
        }

Annoying! Any ideas? Please ask for clarification