Weekend form HK to GZ

Hi,

I am a British passport holder living in Hong Kong with a HKID card.

I would like to go to GZ for the weekend and go via the train from Hung Hom to GZ East railway station.

If I have the return train ticket when entering China is this ok? I ask because it is not a ticket for a 3 country but a return one to my original destination.

Many thanks,
Gary