Conditional Formatting in a Pivot Table to show change week over week

[lpost1214]

Item	Mo/Yr	11/14	11/21	11/28
30020	Jan 17	5000	5000	3500
30020	Feb 17	4000	3500	3500
30021	Jan 17	2000	1800	2500
30021	Feb 17		1800	1750

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Above is a sample data set. I have the data above in a pivot table it represents forecast broken down by item, forecast month, and then the dates running across the top represent a date that a snapshot of the forecast was taken. I'd like to use conditional formatting, preferably showing a cell as orange to indicate up and red to indicate down to the help identify where there are forecast changes week over week.
I.e. i'd want the 3500 for item 30020 in Jan 17 on 11/28 snapshot to show a red down arrow next to it.