Change of Single entry to double entry visa for china upon arrival in china

I am a Indian and is visiting Hefei on single entry visa valid for 3 months from 19 Feb 2013. while returing to india via Guangzhou i would like to spend 2 days in guangzhou(23&24 Feb 2013) and 1 day(25 Feb 2013) in macau. For visiting macau being indian I don't need visa for 1 day but after visiting macau i would like to come back GZ to catch my flight on 26 Feb 2013 to New delhi. can i get changed my L to double entry at Hefei or in GZ?