Would I be able to use the 72 hour waiver?If not could I get another single entry one whilst in PRC?

I am travelling from uk via Amsterdam to Guangzhou (arrive Tuesday 16). I will then be travelling to yunfu, zhuhai and was then hoping to visit Macao on sunday 20 towards the end of my stay. I would leave Macao on the Monday and return to Guangzhou for my early morning Tuesday flight direct to the UK. My problem is that I have only been issued a single entry one. I could get a flight from mhf via Beijing to Guangzhou.