IE Automation - Calling a client JavaScript **method** from server-side C#

Given the following C# code:

    public object CallJavaScriptFunction(string functionName, params object[] args)
    {
        object script = Document.Script;
        var result = script.GetType().InvokeMember(functionName, BindingFlags.InvokeMethod, null, script, args);

        return result;
    }

And the following client-side JavaScript block:

function someFunction() {
    alert('This is only a test!');
}

var someObj = {
    someMethod: function() {
        alert('This is another test!');
    }
}

The following server-side block executes successfully:

CallJavaScriptFunction("someFunction");

But this will throw a DISP_E_UNKNOWNNAME:

CallJavaScriptFunction("someOBj.someMethod");

Obviously I'm doing something wrong here - probably there is another way of calling InvokeMember on JavaScript instance methods, but I was not able to find out how.

Any thoughts? Any help will be appreciated.