Looking for a method to produce side by side list either double triple or quad

I have a csv list from an external source for example containing in date order


To save paper either in portrait have two lists from source
Sourcerow1, sourcerow2
Sourcerow3, sourcerow4

And so on until list1 is exhausted

Now for the criteria I may want to match only on one particular item, held in another cell

In matching on that criteria there may be instances where there might be multiple rows for the same date for that item, in which case I would want to sum the count and post only a single row to my report

I may to do the sum of the count before processing to a new single list to simplify things