I guess I should have added the worksheet name. Each sheet is named Jan 2019, Feb 2019, Mar 2019, etc.
First 3 letters of the month space then current year 2019
But I appreciate the help, I think I know where you're going but the worksheet name with the space in it might need extra work.
I did up to Jun 2019 so the way I do it is copy all the cells in Jun 2019 and paste and into new sheet and manually change all the references to May that June used into the July 2019 worksheet with references to Jun 2019.
=IFERROR((C14/'May 2019'!C14)-1,0) This is the Jun 2019 worksheet, so July worksheet would need to change May 2019 to Jun 2019.
then another formula, =SUM('Jun 2019'!C14-'May 2019'!C14), in July worksheet I would change the months,
=SUM('Jul 2019'!C14-'Jun 2019'!C14)
Thank You for any help clearing this up