Yes, this is possible. If you add the HTC widget "Mobile" this disables use of the Verizon Data network. I turn it off when I don't need data, and just want wifi, or just want to save battery for awhile.

Press and hold empty spot on one of your home screens > HTC Widget > Settings > Mobile Network

now you'll have a widget to simply disable the data usage.

you can also use bluetooth to disable bluetooth, GPS for GPS and Wi-Fi for Wifi. The Airplane mode disables ALL wireless features including voice/txt. The only thing you can't disable on your own is JUST the voice/txt features... but im trying to figure out how to do that.