VBA Excel : Insert Subtotal before every set of unique row data

I'm new to Excel VBA.

Attached is the list of Toll Charge Information for Vehicles. I want to insert blank row before every continuous Vehicle Data (Column D). Also I want to sum the Toll charges (subtotal) of the repeated vehicle to the blank row.

I'm stuck. Can anybody help?

                Sub AddBlankRows()
            '
            Dim iRow As Integer, iCol As Integer
            Dim iRow1 As Integer, iCol1 As Integer
            Dim iSum As Integer

            Dim oRng As Range

            'Set oRng = Range("a1")

            'iRow = oRng.Column
            'iCol = oRng.Column
            iRow = 1
            iCol = 4
            iSum = 0
            iSum1 = 0

            iRow1 = 2
            iCol1 = 4
            Do

            While Cells(iRow1, iCol1) = Cells(iRow1 + 1, iCol1)
                    'iSum = iSum + Cells(iRow1 + 1, iCol1 + 3)
                    iSum = Cells(iRow1, iCol1 + 3)
                    iSum1 = iSum + Cells(iRow1 + 1, iCol1 + 3)
                    iSum = 0
                    iRow1 = iRow1 + 1
            Wend

            If Cells(iRow + 1, iCol) <> Cells(iRow, iCol) Then
                'Do

                 'Loop While Not Cells(iRow, iCol).Text = ""
                'Cells(iRow + 1, iCol).EntireRow.Insert shift:=xlDown
                Rows(iRow + 1 & ":" & iRow + 4).Insert
                    Cells(iRow + 1, iCol - 3).Value = "<table1_Group1 vcTollPoint=""Transactions for Tag # " & _
                    Cells(iRow + 1, iCol - 3).Offset(4, 2).Value & " Plate # " & _
                    Cells(iRow + 1, iCol - 3).Offset(4, 3).Value & """" & " textbox60=""Transactions for Tag # " & _
                    Cells(iRow + 1, iCol - 3).Offset(4, 2).Value & " Plate # " & _
                    Cells(iRow + 1, iCol - 3).Offset(4, 3).Value & ":"" textbox64=" & iSum1
                iRow = iRow + 5
            Else
                iRow = iRow + 1
            End If
            '
            Loop While Not Cells(iRow, iCol).Text = ""
            '
            End Sub