VB.NET WebBrowser InvokeMember on button with no ID

I am currently having trouble finding an element of a button that does not have an ID. The only method I know of is:

webBrowser1->Document->GetElementById("submit")->InvokeMember("Click");

This does not appear to be a form so I am not able to use:

webBrowser1->Document->Forms[0]->InvokeMember("submit");

I've included a screenshot of the button I need to click:

Button on page