Here's how I got it to work (C# version):
If you ever have a need to access properties of a master page from a user control in ASP.NET 2.0, here?s how you do it:
Add to .ASCX file:
<%@ Reference VirtualPath="~/Templates/ListDetailTemplate.master" %>
Cast the reference as follows:
((ASP.templates_listdetailtemplate_master)Page.Master).PageHeightOffset = 250;
Translate that to VB.NET & you should be good to go.
-spencer