Direct Access Setting for a domain with the same domain name as internal as external

Dear all,

I have configured a Direct Access Server on Windows 2008 R2, but my internal domain and external domain have the same name, so When a Direct Access Client is on Internet, the computer thinks that is Inside the network, but obviously it is not there, so how can I manage the External domain, because the Internal domain We can not modify.

We need to get access to internal resources

Regards
Thank you in advanced