@Laughing Man: what you probably want to do is to set up AutoDisconnect as usual (setting low entries for minimum data transfer to keep connection up when only some IM is actve) but disabling switching 2G/3G and manually switching to 3G when higher bandwith is needed. Because no application can look right into your brain and read your wishes you will have to tell the phone when it has to be 3G or 2G.