Are you sure that it's the expiry date parameter you want to change? If so then a script attached to a rule should do the job as the messages arrive e.g.
Sub SetLimitAndSendOnMessage(olItem As MailItem)
Dim olOutMail As Outlook.MailItem
Set olOutMail = olItem.Forward
With olOutMail
.To = "someone@somewhere.com"
.ExpiryTime = Date + 30
.Display
'.Send 'Enable after testing
End With
lbl_Exit:
Set olOutMail = Nothing
Exit Sub
End Sub
You can test the code by selecting a message in your InBox and running the following
Sub testMacro()
Dim olMsg As MailItem
On Error Resume Next
Set olMsg = ActiveExplorer.Selection.Item(1)
SetLimitAndSendOnMessage olMsg
lbl_Exit:
Exit Sub
End Sub