ASP.NET gridview select textbox on focus

I have a gridview on an asp.net webpage which has textboxes as template fields throughout each column.  When the gridview loads most of the textboxes are prepopulated with text.  I would like to be able to click on the textbox and have the text be selected (highlighted) so that when a change needs to be made the visitor does not need to select the text by dragging the mouse or double clicking on it.

I have tried using javascript to accomplish this by placing the following code into the page for a textbox I call tbTest which is OUTSIDE of the gridview (just for testing purposes).

'This is inserted into the source code of the aspx page
 <script type="text/javascript" language="javascript">
          function selectText() {
              document.getElementById("<%=tbTest.ClientID %>").select();
          }
    </script>

'This line is in the page load event of the code behind
tbTest.Attributes.Add("onfocus", "selectText();")

This works on the tbTest textbox but I do not know how to make this work for a textbox in the gridview.  I can access the textboxes by using the following line in the RowDataBound event.

Dim testString As String = TryCast(e.Row.FindControl("tbGridCol1"), TextBox).Text()

Can I add something to the RowDataBound event to accomplish this or is there another method anyone knows of?