Sub Demo()
Application.ScreenUpdating = False
Dim i As Long, j As Long, k As Long, lRow As Long
With ThisWorkbook.Worksheets("Sheet1").UsedRange
  lRow = .Cells.SpecialCells(xlCellTypeLastCell).Row
  For i = 1 To lRow - 1
    For j = i + 1 To lRow
      k = k + 1
      .Range("D" & k).Value = .Range("A" & i).Value & " & " & .Range("A" & j).Value
      .Range("E" & k).Value = .Range("B" & i).Value + .Range("B" & j).Value
    Next
  Next
End With
Application.ScreenUpdating = True
End Sub