Calculate change using pivot table

[radamsperfectserve]

Hello! Wondering if someone can help me achieve the following: I need to quickly be able to find changes between two data sets on a weekly basis. I am currently comparing data from last week to this week manually but I know there has to be a better way. I have put together a pivot table organized by the record ID of my data. I then have added date columns to show when the data was pulled. I am summarizing the value attributed to each record. Now, what I need to know is how to calculate the difference between the columns. 

Any suggestions? This is just the first type of comparison I'd like to run. There are other attributes I would like to compare as well including date fields and text fields. TIA

[#2]

@radamsperfectserve 

Click in the pivot table.

In the PivotTable Fields task pane, click on the value field, and select 'Value Field Settings...' from the drop down menu.

Activate the 'Show Values As' tab.

Select 'Difference From' from the drop down.

Select the column labels field in the 'Base field' list.

Then select (previous) in the 'Base item' list.

Click OK.