Not sure if I understood the problem correctly.
Do you want the calendar on your device to overwrite the ones in Outlook?
I know that you can set it up so that the ones on the device get added to the Outlook and in case it is the same appointment, the device will overwrite the Outlook item. But I don't think I know a way to clean out Outlook entirely.
This is what I do, when I want the device items to be moved into Outlook. I delete the current partnership in ActiveSync. Then re-sync and establish new partnership. You will get prompted for items to sync and also direction, select device to Outlook.
IMPORTANT: Backup the device and backup you Outlook data.
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