This is possible, however, can you provide some answers to a couple of quick questions.

1. You stated you toggle profiles. can you add your iMAP account to your Exchange account so you never have to toggle between the two?

2. Which account was created first?

3. The calendar in your personal folder, is this a shared calendar?

Normally the exchange calendar, or your personal exchange calendar is what your Outlook client defaults too. once you select the calendar you should be able to save by closing the application.

Hope this helps