Your first option goes from today (Date()) back to monday... (Date()-Weekday(date(),2)+1)this weeks orders:
"Between Date() and Date()-Weekday(date(),2)+1"
last weeks orders:
"Between Date()-7 and Date()-Weekday(date(),2)-6"
previous weeks orders:
"Between Date()-14 and Date()-Weekday(date(),2)-13"
Then your second option you want to go back from Monday to previous monday. If you want to go backwards from Monday... you have to use that part of your formula...
Last week: Between Date()-Weekday(date(),2) and Date()-Weekday(date(),2)+1 -7
Or something like that... Then the week before that is -7 and -14
etc.
I agree, maybe you want to make the history be variable.... so that anyone anytime can go to any time in history... 0 beeing this week then 1 for last week, 2 for the week before, 3 before that, etc...
Good luck!