Sub RenameCharacterStyles()
    Dim oldNames As Variant
    oldNames = Array("Old Style 1", "Old Style 2", "Old Style 3")

    Dim newNames As Variant
    newNames = Array("New Style 1", "New Style 2", "New Style 3")

    Dim i As Integer
    For i = 0 To UBound(oldNames)
        Dim style As Style
        Set style = ActiveDocument.Styles(oldNames(i))
        style.Name = newNames(i)
    Next i
End Sub