Calculating week to date comparison

[rebubula]

Hi. I am trying to figure out a formula to compare numbers from the current week against numbers from the previous week. Here is an example of what I need:

Last week
M - 5
T - 4
W - 5
R - 2
F - 3

This week
M - 7
T - 2
W - 4

I want a formula for a cumulative comparison for a sum of the numbers this week to date against the same days from the previous week. So, if I ran the report today, it would show that we are down ~7% from last week. I started with a SUM and tried to nest IF and ISBLANK, but am having no luck.

Any help is much appreciated. Thanks!

 

[Desu Nota from Columbus]

It might be beneficial to either show or tell us which cells the data is in and how the date is set. Is there a date attached to the M-5 or is it any monday?

Example:

Column A
M-4/11
T-4/12
W
Th
F

Column B
#
#
#
#


Perhaps a screen shot of the excel data.