Modify Web.Config Security via Web Form?

Hi, I have an application running with Windows Authentication. Roles have been setup to manage which users can access which forms (locations) using the following code for each section of the program as appropriate:
<location path="Folder1/Page1.aspx">
    <system.web>
      <authorization>
        <allow roles="Role1,Role2,Role3,Role4" />
        <deny users="*" />
      </authorization>
    </system.web>
  </location>
Is it possible to modify the above part of the web.config file using vb.net code on the back of a web form? If so... how?!

Thanks
Matthew



...