General :: Forcing 2G When 3G Not Available

I'd like to know is there some android application that can control my 2G/3G settings based on a rule (something like AutomateIt, which does not do that) so that it stops my phone from trying to connect to 3G network when signal is low or lost?

Let me explain - I go twice a week to a gym which is actually in the basement of a building, and my carrier's network is very weak there, mostly no signal at all. During those 2hrs period I've noticed that my battery drainage is larger than when I'm in the reach of the network.

Since I know that cell phones tries to log-on to the network using maximum power, and that 3G uses more juice than 2G, I concluded that my phone is trying to reconnect to 3G network when it looses signal instead of doing nothing.

Now, I don't exactly know how phones in general behave when they loose signal alltogether (I think they go from 3G down to 2G and then should go into some passive, listening-only mode, waiting for the beacon from the cell tower), but I guess that in such cases it would be better for me to force the phone to go to 2G (and keep reconnecting/listening on 2G) and later on, when it detects 3G, switch back to it.

Unfortunately, Automate It does not have radio control and I can't use it like I do at night to turn off sync and data and turn it on in the morning. Also it does not have a rule related to network signal strength/type/whatever.

I can't use some timer app that would simply turn on/off airplane mode during that period, because I might not go to the gym sometimes, or I might simply be late or leave the gym later, so I'd still have larger battery drainage, even for a short period of time.