Sub matching()
Dim i, j As Integer
i = ActiveCell.Row
j = ActiveCell.Column
While Cells(i, j).Value <> ""
If Cells(i, j).Value = "xxxxx" Then Cells(i, j).Value = "yyyyy" Else
If Cells(i, j).Value = "yyyyy" Then Cells(i, j).Value = "xxxxx" Else
....
....
If Cells(i, j).Value = "bbbbbb" Then Cells(i, j).Value = "ccccc" Else
i = i + 1
Wend
End Sub