Group Gridview Data and bold 1st line of new item type

I have a gridview that displays results which I'd like to bold the first line of each now type of item

EG

See the below file.  The highlighted yellow lines show the 1rst line of each new unit.

How can I do this by Bolding or coloring the first row of each new data item in my grid view.

I thought somthing allong the lines

Sub doColor(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
If e.Row.RowType = DataControlRowType.DataRow Then
   Select Case e.Row.Cells(0).Text 
      Case   "A" 
         e.Row.BackColor = Drawing.Color.Blue
      Case "B"
         e.Row.BackColor = Drawing.Color.Green   ' etc.......
   End Select
End If
End Sub

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