How to pass a JS object from VB.NET?

Using Acrobat X Pro, I want to hand plain Javascript objects from VB.NET to Acrobat JS functions.

For instance (just a snippet):

Dim pdDoc As CAcroPDDoc = CreateObject("AcroExch.PDDoc")

pdDoc.Create()

Dim jsObj As Object = pdDoc.GetJSObject()

Dim newDoc As Object = jsObj.app.openDoc(New With {.bUseConv = 1, .cPath = inputFile})

Last line results in a COM exception: HRESULT: 0x80020005 (DISP_E_TYPEMISMATCH)

In Perl, this is quite easy, according to http://rodriguezlucha.blogspot.de/2012/09/converting-word-to-pdf-using -adobe.html:

my $new_doc = $jso->app->openDoc({

    cPath=>"$input_file",

    bUseConv=>1,

});

What is the according syntax in VB.NET?

Thank you very much!