Create Smaller Structure Based on Larger Structure Indices

I have a large dataset with many fields all correlated by time(each row is correlated). I'd like to separate individual datasets based off known times (indices).

Let's say I have CoreData as the structure, and time, counts, direction as fields, each a 2000x1 double of random numbers:

CoreData.time, CoreData.counts, CoreData.direction, etc.

I know that, since my data is correlated row-by-row, the first dataset is comprised of the rows 5-50 in CoreData, with identical fields.

Ideally, I'd like something like:

FirstDataset(all fields, rows 5-50)=CoreData(all fields, rows 5-50);

Is there an elegant solution? Right now I have all my datasets created with empty arrays, but I'd rather not brute force a for loop with each individual field specified in eval statements.