Sub Button2_Click()
  Dim rng As Range
  Dim i As Long
  Dim a As Long
  Dim rng_dest As Range
  Application.ScreenUpdating = False
  'Check if invoice # is found on sheet "Invoice data"
  i = 1
  Do Until Sheets("Invoice data").Range("A" & i).Value = ""
    If Sheets("Invoice data").Range("A" & i).Value = Sheets("Invoice").Range("D13").Value Then
      'Ask overwrite invoice #?
      If MsgBox("Overwrite invoice data?", vbYesNo) = vbNo Then
        Exit Sub
      Else
        Exit Do
      End If
    End If
    i = i + 1
  Loop
  i = 1
  Set rng_dest = Sheets("Invoice data").Range("D:G")
  'Delete rows if invoice # is found
  Do Until Sheets("Invoice data").Range("A" & i).Value = ""
    If Sheets("Invoice data").Range("A" & i).Value = Sheets("Invoice").Range("D13").Value Then
      Sheets("Invoice data").Range("A" & i).EntireRow.Delete
      i = 1
    End If
    i = i + 1
  Loop
  ' Find first empty row in columns D:G on sheet Invoice data
  Do Until WorksheetFunction.CountA(rng_dest.Rows(i)) = 0
    i = i + 1
  Loop
  'Copy range B16:I38 on sheet Invoice
  Set rng = Sheets("Invoice").Range("B16:E38")
  ' Copy rows containing values to sheet Invoice data
 For a = 1 To rng.Rows.Count
    If WorksheetFunction.CountA(rng.Rows(a)) <> 0 Then
      rng_dest.Rows(i).Value = rng.Rows(a).Value
      'Copy Invoice number
      Sheets("Invoice data").Range("A" & i).Value = Sheets("Invoice").Range("D13").Value
      'Copy Date
      Sheets("Invoice data").Range("B" & i).Value = Sheets("Invoice").Range("F3").Value
      'Copy Company name
      Sheets("Invoice data").Range("C" & i).Value = Sheets("Invoice").Range("B8").Value
      i = i + 1
    End If
  Next a
  Application.ScreenUpdating = True
End Sub