Side by side Custom validation

I have a side by side question similar to the below. Respondents aren’t required to answer all questions, but if they give an answer on a row, then there should be an answer somewhere on the previous row i.e. there shouldn’t be any blank rows followed by a row with data in.

It’s probably possible with custom validation, but because some of the columns have display logic, it’s set up as 9 columns - so doing the validation means checking for a response in each of the 9 cells in the row.

Is there a way to do the validation. i.e.

1. if there are any answers in the second row, then check there are answers in the first row
2. if there are any answers in the third row, then check are answers in the second row
3. etc