Short answer: No you cannot use more than one Internet connection at a time.
Long answer: Maybe, but it depends on the software that you run. If the software allows you to choose a particular network interface (most do not), then you would need to manually configure your software to use one or the other.
of which softwear u talking about.and once accidently i was happen that both the connection was running simultaneously and my speed was 3.8mb(2mb+2mb=4mb)then i dont know what happen after restar the laptop the settings change automatically . from then to now i have tried my best but i m unable to combine both connections .if it is impossible then what was that y my spped was 3.8 mb . plz answer and guide me if u have any type of setting u have in ur mind by use of that i become able to use both connection .. thank i m very tryred plz help me