Need a multiple entry visa as i will be visiting Macau amidst my tour and re-entering Shenzhen?

I will be visiting some cities in Mainland China, one of which is Shenzhen and then to Macau and again re-entering Shenzhen to continue my tour in Mainland China. I see that only single entry is provided for tourists, how do I obtain / justify the need for multiple entry as I have to exit and re-enter to visit Macau?

Thanks in advance