Formatting Issue

Hi,

So I have a template that has a piece of formatting code which I obtained from a different post in this forum. It alternates gray & white on a copy of a pivot table to make it easier to read. Normally there are 5 different Sample Names per grouping but in this one example the user only had 3 so my formatting is off in the end. Would it be possible to get some help with this code to make it more dynamic. I would like that this modified piece of code can either get the number by input from the user or that it can get the number on its own (by maybe counting Vial rows or when there is a repeat in Sample Name) and create the correct formatting no matter how many the user may do? Please advise....

Thank you so much for your assistance.