Convert footnotes to a references field

FootNotes.cls

VERSION 1.0 CLASS
BEGIN
  MultiUse = -1  'True
END
Attribute VB_Name = "ThisDocument"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Sub FootnotesToReferenceField()
    Dim refList As String
    Dim i As Integer
    Dim fn As Footnote

    refList = ""

    For i = 1 To ActiveDocument.Footnotes.Count
        Set fn = ActiveDocument.Footnotes(i)
        refList = refList & i & ". " & Trim(fn.Range.Text) & vbCrLf
    Next i

    SetCustomProperty "FootnoteList", refList
End Sub

Sub SetCustomProperty(propName As String, propValue As String)
    Dim props As DocumentProperties
    Dim p As DocumentProperty
    Set props = ActiveDocument.CustomDocumentProperties

    On Error Resume Next
    Set p = props(propName)
    If Err.Number <> 0 Then
        Err.Clear
        props.Add Name:=propName, LinkToContent:=False, Type:=msoPropertyTypeString, Value:=propValue
    Else
        p.Value = propValue
    End If
    On Error GoTo 0
End Sub