Changing the internal audit schedule

I have had conflicting responses to this question. Is there any requirment for either ISO 9001 or the QSR that the internal audit schedule be a controlled document? I find for various reasons that I have to change the dates (never moved up, always moved back) of several internal audits per year. Currently I initial and date on the schedule if I need to reschedule but if the schedule is controlled, I would need to initiate a change order each time and that could be a headache. comments?