Wireless, how to use dual band

Hi, I have few laptops and two routers with dual band (TP-LINK TL-WDR3600 N600 WIRELESS DUAL BAND GIGABIT ROUTER) . What i am trying to achieve is if someone want to send msg to a an individual then one of the band should be used (eg 2.4GHz) and if someone want to send message to the group then it should be send through another band (eg 2.8GHz or 5 GHz). How can i do that.? I have created a mesh network and written a simple client server applications through which all laptops communicate. Sorry if this is not the correct mailing list Regards