Need help to sum live data in 2 week increments.

[idoon3y]

My goal is to understand which two week increments of a marketing campaign were most/least effective.

Column A: live data for a marketing campaign (leads generated)

Column B: Sum up the live data up until 2 weeks after the start date of the campaign. After the 2 weeks is complete, I would like this data to “stay” in the cell and not disappear after the 2 weeks is over.

Column C: Sum up the live data from weeks 3-4 of the campaign. After the 4th week is complete, I would like this data to “stay” in the cell and not disappear after the two week span of weeks 3-4 is over.

Column D: Sum up the live data from weeks 5-6 of the campaign. After the 4th week is complete, I would like this data to “stay” in the cell and not disappear after the two week span of weeks 5-6 is over.

I would like this to continue until weeks 15-16 of the campaign.

I have tried the following formula, but this makes it so the values disappear after the 2 week period is over.

- Where B4 is the date 2 weeks after the start date and A7 is the live data I want to input

=IF(TODAY()<=$B$4,SUM(A7))

Does anyone know of any ways to make this possible or easier?

I would really appreciate any help!