Update an app from other iTunes/Computer without losing the Documents folder

Our inHouse tech have installed our own app to some of our iPods 3.x devices.

Now, we have to update that app but WIHTOUT LOSING开发者_运维技巧 the data that has been entered by users.

The problem is that the computer who installed those app and syncronyzed, isn't working now, and when we try to update them from another computer, iTunes insist in deleting ALL apps and documents app from iPods and add the new ones.

I suppose that this action will erase ALL documents from the app, so we will lose the data.

What can we do ?

thanks,

m.

ps. those devices have currently an AdHoc profile

You can try to use the iPhone Configuration Utility, which can be found at http://support.apple.com/kb/DL851