How to keep columns in a summary pivot fixed when the columns are variable

[KarenHM]

Hi

I have a job and I created a formula with  IF (if any information in the data is "invoices NM" then "Invoices AP" ..... and then with this information i created a summary pivot , but now one o the field that I set up in the IF doesn't have information this period. At the end I have another formula that sum all the columns that has the summary pivot, but appear and error because this column doesn't exist this period. 

do you know how can fixed some columns in case that a specify period don't appear?

If 

This month dont appear Purchase invoices then AP Constab dont appear here

so I cant do this sum 

I appreciate the support that you can give me !

[dougperez]

You can try to use Multi-field formula tool with "dynamic or Unknown fields".

[Qiu]

@KarenHM 
There are maybe other more dynamic way of doing this, but should invove dramatic change of your current flow.
With minimun change, I think we can do like below given you have known your necessary columns.
Idea is add the missing column as empty column to the orginal data input.