Storing in web.config password MD5?

Hello everybody...
 
I want to ask i have this code for generate password using MD5
strHashValue = FormsAuthentication.HashPasswordForStoringInConfigFile(TxtPassword.Text, "MD5")
And i want to save this password for web.config to update old password?
My web.config like this
 <authentication mode="Forms">
      <forms>
        <credentials passwordFormat = "MD5">
          <user name ="admin" password ="6034856155F4D9255CA0160FD66F9B25"/>        
        </credentials>
      </forms>      
    </authentication>  
 
and i want to update this password direct ...