There are unconfirmed reports from DigitalPoint Forums that Microsoft is going to upgrade adCenter soon to support daily budgeting.
Currently, I believe, adCenter only has a way to set a budget at the month level. You can supposedly set a "daily limit" but that will pause your campaigns based on the monthly average.
This new feature should give advertisers more granular control over their campaign finances.
Forum discussion at DigitalPoint Forums.
