Integration Services :: SSIS Custom Task - Drop Down List In UI Window

I'm writing my first SSIS custom task. I have added Public properties, which appear in the standard task properties window, and to one of them I have added an EditorAttribute as follows:

    <Category("General"), _
    Browsable(True), _
    EditorAttribute(GetType(UIFileNameEditor), _
    GetType(System.Drawing.Design.UITypeEditor))> _
    Public Property FilesToArchive() As String

[Code] ....

When I select the FilesToArchive property in the Properties window, I get an ellipsis that appears in the property value. When I click on the ellipsis, it brings up the FolderBrowserDialog, which is defined in the UIFileNameEditor class. This all works fine.

What I want to do is to bring up the EditorUI, the one you get when you double click on the task, and also populate that with properties which can be edited. I have a class which inherits DTSBaseTaskUI, which is displayed when I double click on the task.

I can also get properties to be displayed in that UI but I cannot get them to be editable in that UI, using the same technique as in the standard Properties window, as described above.