How To Insert 3 Rows and Total

 I've been knocking myself out since yesterday trying to figure something out.  I have some self-taught experience with VBA macros in Excel, but just can't get this.  And I bet it's simple.  Here's the deal:

I have a monthly spreadsheet that lists users and their cell phone expenses.  There is typically 4 - 6 rows for each user.  I want to write a macro that will look at the cell that contains the name, compare it to the cell below it.  Then if they match, move down one cell and compare again.  Then when it fines a difference, add 3 rows, put a subtotal under the expense cells; and then go back to analyzing the name cells looking for the next break and resume.

Is that confusing?  Would anybody be able to help me out with this ...I'd be very greatful!

Thanks

Public Sub ProcessData()
Dim i As Long
Dim LastRow As Long

    With Application
        
        .ScreenUpdating = False
        .Calculation = xlCalculationManual
    End With
    
    With ActiveSheet
        
        LastRow = .Cells(.Rows.Count, "A").End(xlUp).Row
        For i = LastRow + 1 To 3 Step -1
        
            If .Cells(i, "A").Value <> .Cells(i - 1, "A").Value Then
            
                .Rows(i).Resize(3).Insert
                .Cells(i, "B").FormulaR1C1 = _
                    "=SUMIF(R2C1:R[-1]C,""" & .Cells(i - 1, "A").Value & """,R2C:R[-1]C)"
            '    i = i + 1
            End If
        Next i
        
    End With
    
    With Application
        
        .Calculation = xlCalculationAutomatic
        .ScreenUpdating = True
    End With
    
End Sub

 Thanks!!