Visual Basic.NET - Sumar datos repetidos de un datagridview

Dim Codigo2 As String

Dim x2 As Integer

Dim total As Double = 0

Dim fila As DataGridViewRow = New DataGridViewRow

Dim totals As Double = 0

Dim filas As DataGridViewRow = New DataGridViewRow

For x2 = 0 To ClasificacionesDataGridView.Rows.Count - 1

	Codigo2 = ClasificacionesDataGridView.Rows(x).Cells(4).Value  'donde (0) es la columna a recorrer

	If ClasificacionesDataGridView.Rows(x).Cells(4).Value = "marcos" Then

		For Each fila In ClasificacionesDataGridView.Rows

			total += Convert.ToDouble(fila.Cells("DataGridViewTextBoxColumn5").Value)

		Next

		Dialog1.Label1.Text = Convert.ToDouble(total)

	End If

Next