Tracking Last Row That Changes

Hello, I am currently running a project based on an excel template with 38 rows. However, the number of rows can increase based on the customer and how many invoices they have. Is there a way of knowing what the last row is after it has completed inserting the number of invoices. So for example if it goes from 38 to 61 invoices is there a way to tell the program the last row is 61 so I can write the total sum in that cell

? Thank you

Note it Please.

Hi @jhj3627 thank you however it is a bit tricky because the program is constantly creating invoice excel files based on the customer so the read range always changes. Would there be a way of keeping track of each individual excel file and maybe setting a boolean for when it completes looping for a specific customer so it doesnt continue counting for a different customer? Thank you. Range