Can I set an instance property in Javascript on a Scriptable Member property in Silverlight?

I have the following (2) 'ScriptableMember' types in my Silverlight control:

<ScriptableMember()>

Public Property MType As MyCustomType



<ScriptableMember()>

Public Property Message As String

The purpose here is obviously to allow exposure via the HTML bridge in Javascript. Calling the 'Message' property is trivial and works perfectly like below:

var SLControl = document.getElementById("SilverlightControl");

SLControl.Content.MyRegisteredControl.Message = 'Hello';

However I am having trouble setting the values of an instance property by drilling down to its properties in JS. The code I would think should be as below:

SLControl.Content.MyRegisteredControl.MType.Name = 'John';

Notice how I added in the 'MType' and then accessed one of its Public Properties named 'Name'. The MyCustomType class has all the appropriate 'ScriptableMember' atributes as required.

However when that line above is ran I get the following error:

"Microsoft JScript runtime error: Object doesn't support this property or method"

It works just fine on the assignment of 'Message'. Is it possible in JS to drill down through an instance property and assign its variables? If so do I have the JS incorrect, or what do I need to do to fix this. Thanks!