Auto update task priority as due date approaches

Hey,

I have some sort of a personal "backlog" by giving my tasks priorities. Highest prio means "within a week", second highest means "within a month", normal prio means "within a year", low prio means "at some point in my life".

I'd like my tasks to automatically move to the highest priority when their due date is within a week.

Would be even better if my "sort by priority" view would treat due date as a second key.