Are you looking for the average number of entries per week or the total number of entries per week? If wanting the total number per week, you could add a Chart element with your date field bucketed by week. If you're looking for the average, could you let me know how you are hoping to calculate that number? Would you want to count the total number of records per month and divide that by 4? If so, you could use a combination of Count fields and formula fields to obtain the average then use that field in a Number element in your interface.
