Fitting External GSM Antenna..?

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Hi guys,

I've been tasked to fit a circuit with the option for an external GSM antenna, it currently has an internal one. Before I do anything stupid the attached pic shows what I'm about to do...

http://i.imgur.com/hwBhhWn.jpg

So drilling through the track that connects to the internal antenna and fitting a socket for an external one. Now will this do what I want or completely stuff it? will the internal one still work as was when the aerial is not attached? etc..

If I'm doing it wrong what is the suggestion?

Thanks.