I have a VB.net class registered for COM interop which I'm instantiating within an HTML page using the following code: I can call methods on it just fine, but suppose I want to set a javascript function as a property, like so: MyClass.TestFunction = function () { alert("It worked!"); } How would I set my vb.net code up to be able to fire that function? This is how MSXML works in javascript for XMLHttpRequest objects, you can set XHR.onreadystatechange = function () {} I'm looking for a similar implementation in my class.