Hi Mariah,
If you set the Date of Activity constraint to "between", then you can specifiy the exact dates. Just choose the first day of the week and then the last day of the week:
If you're saying that you want to see the highest number of web page visits which occurred during any given week, then your only option is to create a different smart list for each week in the manner I described above, and then look for which one has the most leads.