A UDF

'-----------------------------------------------------------------
Function DocProps(prop As String)
'-----------------------------------------------------------------
  Application.Volatile
  On Error GoTo err_value
  DocProps = ActiveWorkbook.BuiltinDocumentProperties _
  (prop)
  Exit Function
err_value:
  DocProps = CVErr(xlErrValue)
End Function

and enter in a cell such as
=DocProps ("last author")
or
=DocProps ("last save time")

Not "modified date" but you can have last save date/time entered in a cell.

Basically the same thing because a "save" is a modification.

You will need a User Defined Function.

Function DocProps(prop As String)
   Application.Volatile
   On Error GoTo err_value
   DocProps = ActiveWorkbook.BuiltinDocumentProperties _
   (prop)
   Exit Function
err_value:
   DocProps = CVErr(xlErrValue)
End Function

Enter in a cell one of the below...............

'=DOCPROPS("author")
'or
'=DOCPROPS("last save time")
'or
'DOCPROPS("creation date")

For a list of all built-in Document Proerties, run this macro after copying the
DocProps function to a general module in your workbook.

Paste the macro into the same module.

Sub documentprops()
'list of properties on a new sheet
rw = 1
Worksheets.Add
For Each p In ActiveWorkbook.BuiltinDocumentProperties
   Cells(rw, 1).Value = p.Name
   Cells(rw, 4).Value = "=DocProps(" & "A" & rw & ")"
   rw = rw + 1
Next
End Sub

Gord Dibben  MS Excel MVP