MessageBox Not Working When Checking InnerText On WebBrowser

I cannot get the messagebox to show up on my screen when the program checks the text fields on the webpage that says "this is the test".

Here its the code:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If WebBrowser1.Document.Forms(0).InnerText = "this is the test" Then
MessageBox.Show("worked!")
End If
End Sub

How to make the messagebox to show up on the screen when the program checks the text fields on the webbrowser by on the webpage?