What version of Documaker?
You say it needs to be dynamic, but do you have a fixed width or fixed height? Maximum number of columns? Your example shows six columns (3 pairs) is this the structure you want with dynamic row counts?
I am not sure about XML extracts. Hope this hint may help. If the data is in flat file something like below, you can code the 6 fields in one section (since it is fixed), with section level overflow selected and Overflow Multipliar as 3. For first pair of Year & Dep%, the Record should be 1. For second pair the Record should be 2 and for third it should be 3. Trigger the section using the regular conditions.
It sounds like you have created a "line" or "row" section with the 6 fields (3 sets of 2) on it. That is fine.
Then you would create a trigger to calculate your total occurrences, divide by 3 (add 1) and then return that as your trigger count. This will get you enough rows for your content.
Within the "row" section you have, you would add the appropriate xPath or XDD reference to the field rule section. Then review the help on the Overflow and Overflow Multipliers. Essentially, you want the overflow per section and a multiplier of 3 (I think) since you have 3 sets per section.
Don't just do a search in the help for Overflow because you will see all different kinds that have existed over the years. You want to see the Overflow Multiplier definitions in the Fields section under rules.