Hi Ben
sorry you didn't tell us what you want to do.
You vaguely showed us your failed try of implementing it.
With that I cannot help you.
Why do you want to loop over the same data again?
Why do you loop over the data at all?
What exact operations you want to do on the data?
As long as we don't know the answers to these questions, the only hint I can give you is: the fastest way to do something is to not do it at all 
- Lars