Marcus:
You're on the right path. The only place (that I am aware of) that IVM will read-out a variable is under the OGM advanced tab. To accomplish what you are trying to do, follow these steps.
1. Create yourself an OGM2 that is run after your OGM1.
2. Place in the scripts/notes "The balance is".
3. Select the Advanced tab.
4. Check the Read Out Number After OGM box.
5. In the Variable name field, type in: balance
6. Make sure the Text-to-speech voice synthesis box is checked.
Good Luck