Hi Mark,
This will definitely work.
Right click your check boxes and choose Brower tab and make sure they are set to "Always" post back. That should fix it while the form is open.
When the form reopens, your conditional formatting should work just fine. If not, check the values of the check-boxes. Perhaps it's the difference between TRUE/FALSE, and 1/0.
Please feel free to email us and we can help in real time.
Cheers,