Horizontal Roll up of Weekly Data to Months

[Roselaneess]

Hi All,

I have a forecast report that has dated weeks horizontally across the top with items vertically down the left side and data for each item under each week's column heading. I want to be able to roll up the weeks by the proper month and the data for each of the items also summed for each month.

Ideally I want to be able to replace the data and dates each time and have Excel roll it up for me to the proper month with the sums for each item for that month.

I have attached a file that has the data in the upper portion and the desired result under it.

Thank you in advance for any help.

Barb