Treat an Excel workbook as a 2-dimensional array, and iterate over it.

iterate-2d.bas

Range("A1").Select
Range(ActiveCell, ActiveCell.CurrentRegion).Select

For Each row In Selection.Rows
  Dim rowStr As String

  For Each col In Selection.Columns
    rowStr = rowStr & Cells(row.Row, col.Column)
    If col.Column < Selection.Columns.Count Then
      rowStr = rowStr & ","
    End If
  Next
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