Steven,
Open up the VBA editor (Alt + F11)
Right Click on "ThisWorkbook" in the "Projects" window.
Select Insert/Module
In the module that appears on the right, copy and paste Bob's code:
Function DocProperty(property As String)
DocProperty = ActiveWorkbook.BuiltinDocumentProperties(property)
End Function
Now go back to the workbook and type the following in any cell:
=DocProperty("Last Save Time")
John