Hi there @89trunks ,
if I got you right you can avoid loops in this case. So by using Moving Aggregation node you can calculate Cumulative sum i.e. in which row index each file ends. Then transform those numbers into variables and feed them into Column Expressions or Rule Engine node where you apply your logic with simple Ifs. After that use Cell Replacer node to add file name.
If you really want to use loops then recursive loop after Table Row to Variable Loop Start would probably do the job.
Here is workflow on KNIME Hub to check it out.
Br,
Ivan