Add an Microsoft Project automatically allocated "Permanent ID" Number field that is unique (never reused) and survives task cut and paste operations.

clsPermanentID.cls

'
' The MIT License (MIT)
' Copyright (c) 2013 David Robert Pratten http://davidpratten.com
' 
' Permission is hereby granted, free of charge, to any person obtaining a copy
' of this software and associated documentation files (the "Software"), to deal
' in the Software without restriction, including without limitation the rights
' to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
' copies of the Software, and to permit persons to whom the Software is
' furnished to do so, subject to the following conditions:
' 
' The above copyright notice and this permission notice shall be included in
' all copies or substantial portions of the Software.
' 
' THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
' IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
' FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
' AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
' LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
' OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
' THE SOFTWARE.
'
' ===========================================================
' Add an MS Project Permanent ID Number field 
' that is unique and survives task cut and paste operations.
' ===========================================================
'
' Security
' --------
' After installing this Permanent ID macro, depending on your security settings, MS Project 
' may ask you to enable macros.
'
' Compatibility
' -------------
' Uses standard VBA functions available in recent versions of MS Project. Tested on versions 2007 and 2010.
'
' Installation
' ------------
' The instruction steps are illustrated here: 
'    http://davidpratten.com/2013/11/30/configuration-management-and-ms-project/
'
' In short
' 1) Add this code to a new "Class Module" called "clsPermanentID" in the project file.
' 2) Add the following lines of code in the "ThisProject" object under "Microsoft Project Objects"
'       and uncomment the code from the bottom up. If you uncomment from the top down,
'       VBA will insert unwanted code.
 
' --------- Code Start --------------
'    Dim X As New clsPermanentID
 
'    Sub Initialize_App()
 
'        Set X.App = MSProject.Application
'        Set X.Proj = Application.ActiveProject
 
'    End Sub
 
'    Private Sub Project_Open(ByVal pj As Project)
'        Call Initialize_App
'    End Sub
' --------- Code Finish --------------
 
' 3) Rename one of the custom number fields "Permanent ID", any one will do
' 4) Close and Reopen the project file.
' 5) Now all items in this project file will have a "Permanent ID" assigned that 
'    will survive cut and paste operations.
'
' Retrofitting to existing project
' --------------------------------
' As above, except that for existing tasks, you will need to manually copy current "Unique ID"s into 
' the "Permanent ID" column.
 
Public WithEvents App As Application
Public WithEvents Proj As Project

Sub App_ProjectBeforeTaskChange(ByVal tsk As Task, ByVal Field As PjField, _
    ByVal NewVal As Variant, Cancel As Boolean)
    Dim PermanentID As Long
    PermanentID = FieldIDofPermanentID()
    If PermanentID <> 0 Then
        If tsk.GetField(PermanentID) = 0 Then
            tsk.SetField PermanentID, tsk.UniqueID
        End If
    End If
End Sub
 
 
Private Function FieldIDofPermanentID()
  Dim i As Long
  Dim PermanentID As Long
  PermanentID = 0
  Const PermanentIDFieldName As String = "Permanent ID"
  For i = pjTaskNumber1 To pjTaskNumber5
    If CustomFieldGetName(i) = PermanentIDFieldName Then
        PermanentID = i
        Exit For
    End If
  Next
  If PermanentID = 0 Then
      For i = pjTaskNumber6 To pjTaskNumber20
        If CustomFieldGetName(i) = PermanentIDFieldName Then
            PermanentID = i
            Exit For
        End If
      Next
  End If
  FieldIDofPermanentID = PermanentID
  End Function