access sub elements of membership provider

Greetings!!
I want to access sub element of membership element in web.config through programming. Kindly tell me how I can access and change the settings programmatically. e.g. in the code below I want to access maxInvalidPasswordAttempts,  minRequiredPasswordLength etc. and update through a web form. Please help.
<membership>
<providers>
<clear />
<add name=”AspNetSqlMembershipProvider”
type=”System.Web.Security.SqlMembershipProvider, System.Web,
Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a”
connectionStringName=”LocalSqlServer”
enablePasswordRetrieval=”false”
enablePasswordReset=”true”
requiresQuestionAndAnswer=”false”
applicationName=”/”
requiresUniqueEmail=”false”
passwordFormat=”Hashed”
maxInvalidPasswordAttempts=”5”
minRequ ...