The short answer is to look at the windows available for a process and check the titles to see if it's the page you want.
If System.Diagnostics.Process.GetProcessesByName("firefox").MainWindowTitle = 'My Page Title'
...
End If
That said, there are much better ways to do this - If you're using firefox, look into GreaseMonkey, if in Chrome, look at TamperMonkey.
Both allow you to inject custom javascript into any page whose url matches a pattern you choose. In effect, you could write some Javascript to submit a form (say) 30 seconds after page load.
This would have the benefit of working if a different tab is selected as well as not requiring a whole application.