[mecreyes]

I feel your pain. I do not have a solution in terms of a software "switch".

But I do use this little trick that prevents unnecessary connections. All you have to do is set up a password for your CDMA connection, then when your phone wants to connect it will prompt you for your password. I left all the fields blank, so that all you have to choose is "OK" to connect or "Cancel" to dismiss the request. It will not connect until you make a choice. To do so, follow these steps:

Start
Settings
Connections Tab - Connections
select "Manage Existing Connections"
Select your Data connection (it has number #777) - Then hit EDIT
Click Next past the screen "enter a name for the connection"
Click Next past the screen "Enter the number exactly as it should be....."
You will now come to the screen to set a User name and password.
*Leave all fields Blank" - (or fill them in if you want to, I prefer blank)
Click Finish - You are Done!!

Now whenever your phone seeks to make a connection it will prompt you for your username and password. Assuming you have left/set the fields blank, then all you have to do is make the choice between "OK" to connect, or "Cancel" to dismiss