Hi,
You will need to do it with JavaScript and then call WebView.EvalScript to run the script. For example, the following code would set a textbox's value:
Code: C#
webView1.EvalScript("document.getElementById('textbox1') = 'abc';");
Here the JavaScript code is:
Code: JavaScript
document.getElementById("textbox1").value = "abc";
That's the code that actually set the textbox's value. For other task is the same. The basic rule is for anything outside of the WebView, you do it using your .NET code (C#/VB), for anything inside the WebView you would do it through JavaScript.
Hope this helps. Please feel free to let us know if you have any more questions.
Thanks!