Try this:

Sub Test()
Set MyObj = CreateObject("Excel.Application")
'MyObj.Visible = 1
MyObj.Workbooks.Open ("C:myfile.xls")

c = MyObj.Workbooks(1).CustomDocumentProperties.Count

For Each prop In MyObj.Workbooks(1).CustomDocumentProperties
n = prop.Name
v = prop.Value
MsgBox n & "=" & v
Next
MyObj.Quit
Set MyObj = Nothing
End Sub