I have a study visa in HK for 5 months and I applied for a double entry permit to Mainland China.

I have already used one entry to Beijing and I would like to use the secondo one to Guilin in three weeks. However, next Saturday I want to go to Shenzehn, too. Can I get an entry permit to Shenzhen at the border and use the left entry to Guilin or will I have to use the secondo entry left to go to Shenzehn?