T4 Text Template - generate a part of web.config with tt

Question

I have a big solution with so much WCF services, and my web.config file (in particular the system.servicemodel part) was too big, so i divide the 4 sections of my part in this way

<system.serviceModel>
   <extensions configSource="extensionsTextTemplate.config" />
   <services configSource="servicesTextTemplate.config" /> 
   <behaviors configSource="behaviorsTextTemplate.config" />
   <bindings configSource="bindingsTextTemplate.config" />
</system.serviceModel>

now i'd like to know how can i configure my .tt files so that when I modify something they modify the .config files.. can anyone help me?? sorry for my bad english