Private Sub Document_Close()
   Dim sColor As String

   sColor = ComboBox1.Value
   Me.CustomDocumentProperties("SelColor") = sColor
End Sub

Private Sub Document_Open()
   Dim oProp As DocumentProperty
   Dim iCtr As Integer
   Dim vColor, vColors
   Dim bPropExists As Boolean

   vColors = Array("Green", "Red", "Blue")

   For Each vColor In vColors
      ComboBox1.AddItem vColor
   Next

   ' Check if property exists
   If Me.CustomDocumentProperties.Count > 0 Then
      Set oProp = Me.CustomDocumentProperties.Item("SelColor")
      If Not oProp Is Nothing Then bPropExists = True
   End If
   
   If Not bPropExists Then
      ' Add property to collection
      Me.CustomDocumentProperties.Add "SelColor", False, _
          msoPropertyTypeString, "Green"
      ' set default selection
      ComboBox1.ListIndex = 0
   Else
      For iCtr = 0 To ComboBox1.ListCount - 1
         If ComboBox1.List(iCtr) = oProp.Value Then
            ComboBox1.ListIndex = iCtr
            Exit For
         End If
      Next
   End If
End Sub