how to add dynamic rules based on user input to webconfig ?

Question

I want to add a rule, the location path and allow roles determined based on user input .. example TextBox1 to provide location path and textbox 2 to provide a rule for the user.

I want the results in a web config as below:

 

<location path="Report/Default.aspx">
 <system.web> <authorization> 
	<allow roles="USER"/>
 </authorization> </system.web> 
</location>

so far my c # code like this:
 but I am confused to apply as I want :
 protected void AddRoleRule(string location, string selectedrole){        
Configuration config = WebConfigurationManager.OpenWebConfiguration(Server.MapPath("~/Web.config"));
 XmlDocument xDoc = new XmlDocument();         
xDoc.Load(config.FilePath); 
//if the rule exists update the rule 

 //create location element and the path attribute with it's value set to the
 //selected page
XmlElement newLocationelement = xDoc.CreateElement("location");
XmlAttribute newLocationAttrib = xDoc.CreateAttribute("path"); 
newLocationAttrib.Value = TextBox1.Text;
 newLocationelement.Attributes.Append(newLocationAttrib); 
 XmlElement newSystemWebelement = xDoc.CreateElement("system.web");
 XmlElement newAuthorizationelement = xDoc.CreateElement("authorization"); 
//create the allow element  
XmlElement newAllowelement = xDoc.CreateElement("allow"); 
  XmlAttribute newAllowAttrib = xDoc.CreateAttribute("roles");
 newAllowelement.Attributes.Append(newAllowAttrib); 
//create the deny element 
  XmlElement newDenyelement = xDoc.CreateElement("deny");
 XmlAttribute newUsersAttrib = xDoc.CreateAttribute("users"); 
newUsersAttrib.Value = "*";
 newDenyelement.Attributes.Append(newUsersAttrib);
 newAuthorizationelement.AppendChild(newAllowelement); 
newAuthorizationelement.AppendChild(newDenyelement); 
 newLocationelement.AppendChild(newSystemWebelement); 
newSystemWebelement.AppendChild(newAuthorizationelement);
xDoc.DocumentElement.AppendChild(newLocationelement); 
 xDoc.PreserveWhitespace = true; 
//write to web.config file using xml writer 
 XmlTextWriter xwriter = new XmlTextWriter(config.FilePath, null); 
 xDoc.WriteTo(xwriter);
xwriter.Close(); 
 }