.NET: How do I customize bookmark/navigation pannel (e.g. to apprear on the right side)?

Q: When I run my .NET clinet app in a right to left environment, the nav panel still appears on the left and the menu and tool bar are also left justified and not reversed. In short, it doesn’t appear to support RTL. Do you plan to support RightToLeft? I am mostly concerned with the NavPanel; I will not be showing the menu or tool bar in the control.

A: The control does not support adjustments on the built-in navigation menu, however you can easily replace it with your own implementation.

For an example, please take a look at ‘PDFViewForm.cs’ in PDFView sample project (http://www.pdftron.com/pdfnet/samplecode.html#PDFView). The code surrounded with ‘CUSTOM_NAV’ directive adds a custom navigation panel. To enable this feaure simply declare CUSTOM_NAV in the project solution.

I read the answer, but I am not understand which file I declare CUSTOM_NAV. I tried to declare it on PDFVIewFrom.vb, but it generator an error that is "Type ThumbView’ is not defined. Would you tell me the correct page for declaration. Thanks.