Hi,
You can use two methods. The first is by using Page.Master.FindControl('controlID'). Then you can cast it to the type of your user control. The second method is by adding a <%@ MasterType VirtualPath="" TypeName=""%> tag to your aspx page. In the VirtualPath add the virtual path to the master page, and the class in the TypeName. You can then access everything with intellisense.