When are the file's OLE Custome Properties?

[kerendot]

Hi,
My company's product can add Custom Properties to many types of files.
For example, after it adds properties to a *.docx file, they can be viewed through the "File Properties" dialog (in the "custom" tab).
The same way, it adds properties to *.vsd files.
Unfortunately, Visio files don't have the "custom" tab in the "File Properties" dialog - so I started wondering where exactly is this information stored??
I used a separate application to ensure that the file indeed contains the OLE custom properties - see picture.
(link to this application: http://www.microsoft.com/en-us/download/details.aspx?id=8422)

I want to access these properties through Visio U/I (and display them on the drawing).
I tried to search the ShapeSheet area but found nothing (see picture).
Is there anywhere else I can look for these properties?

Thanks in advanced.
Keren

[JuneTheSecond]

This dialog does not seem a Visio dialog, but a file dialog in Windows' file system.
When you search with "Custom tab in file properties dialog" in the web,
some documents said user can add tubs.
However, I think it may need lot of works.

[JuneTheSecond]

If you are using Visio 2013 in Windows 8.1
custom properties are in the sub file, custom.xml.

1. Save your Visio document as vsdx or vsdm.
2. Change file extension into zip.
3. Double click zip file.
4. Double click docProp folder.
5. Copy custom.xml to your work space.
6. Open custom.xml with xml editor like XML notepad.