Numbering Sequence based on two criteria.

Hello daffodil11 and benishiryo...

I am glad to receive your help. Both answers are of great help. But the formulas counts the max of serials in each box. I need to assign sequential numbering to each box of the RMA.

I modified a little bit the reference file so you can see what the goal is. Column E (RMABox) must look like Column D.

I really appreciate your time and effort.

SamCV.
Matamoros, Mexico.