You can build this multi-day timer with the Sequencer Object. You can have up to 100 states in this object. You will use one state for each state of the device, i.e., if the Device is On for some duration an a given day and then Off, you will represent this by two states.
The Sequencer can be in each state until either the TimeLimit is expired or a GoTo is triggered for it. See Online help on this Object for details.
Of course, the assumption here is that this multi-day timer behavior though differs from day-to-day, it is fixed for the week. This way, the Sequencer can go back to the first day after cycling through the days.
Hope this gives you some ideas.