I have experienced the same issues other people have. So I will try to comprehensively cover how I addressed it.
First of all, you have no other option than writing a function meant to get whatever you put in a custom or built-in property and make the "problem" cell to point at it this way:
=yourPropertyGettingFunctionName(PropertyName)
PropertyName being a string referring to the name of the custom/built-in property whose value you want to be shown in the cell.
The function could be written (as formerly suggested) as:
Public Function StdProp(ByVal sPropName As String) As String
Application.Volatile
StdProp = ActiveWorkbook.BuiltinDocumentProperties(sPropName).Value
End Function
for a built-in property, or as:
Public Function UsrProp(ByVal sPropName As String) As String
Application.Volatile
On Error GoTo UndefinedProp
UsrProp = ActiveWorkbook.CustomDocumentProperties(sPropName)
GoTo Exit
UndefinedProp:
UsrProp = "n/a"
Exit:
End Function
As already mentioned, including Application.Volatile will allow for a semi-automatic cell contents update.
However, this poses a problem on its own: whenever you open your Excel file, all the cells using such a relationship will get updated and, by the time you exit the file, Excel will ask you for your permission to update it, no matter if you did introduce any change on it or not, because Excel itself did.
In my development group, we use SubVersion as a version control system. In case you inadvertently hit "update" on exit, SVN will notice it and next time you want to commit your changes, the excel file will be included in the pack.
So I decided to use everything at hand to do whatever I needed and avoid, at the same time, this self-update effect I didn't want.
That means using named ranges in combination with property accessing function/s.
Given the fact I can't expect old files to have provision for my new needs, I wrote this function:
Private Function RangeAssign(sRange As String, sValue As String) As Integer
Dim rDest As Range
If RangeCheck(sRange) Then
Set rDest = Range(sRange)
Else
Set rDest = Application.InputBox(sMsg + vbCrLf + vbCrLf + _
"Please, select a cell to get" + vbCrLf + _
"the name " + sRange + " assigned", sCopyRight, Type:=8)
rDest.Name = sRange
End If
rDest.Cells(1, 1).NumberFormat = "@"
rDest.Cells(1, 1).Value = sValue
RangeAssign = True
End Function
It allows for a proper selection of the destination cell. When assigning values to a property (let's say "Author", which happens to be a built-in one), I also update the value stored in the named range, and can write in a cell:
=Author
if I happen to have defined a range named "Author" and filled its "A1" cell with the value for built-in property "Author", which I need to have updated for our own external tracking purposes.
This all didn't happen overnight. I hope it can be of some help.