Sub ContactChangeNumbers()
    Dim myOlApp As Outlook.Application
    Dim myNamespace As Outlook.NameSpace
    Dim myContacts As Outlook.Items
    Dim myItems As Outlook.Items
    Dim myItem As Object
    Set myOlApp = CreateObject("Outlook.Application")
    Set myNamespace = myOlApp.GetNamespace("MAPI")
    Set myContacts = myNamespace.GetDefaultFolder(olFolderContacts).Items
    Set myItems = myContacts.Restrict("[LastModificationTime] > '01/1/2003'")
    For Each myItem In myItems
        If (myItem.Class = olContact) Then
            If Mid(myItem.MobileTelephoneNumber,  1 ,  1 ) =  7  Then
                myItem.MobileTelephoneNumber = "8" & Mid(myItem.MobileTelephoneNumber,  2 )
            End If
        End If
    Next
End Sub