Splitting a dataset sorted on two fields, based on a change in value in one field

[baradhwaj.h]

Hi,
I am new to MS Access, and am not sure if what I want to do is even possible. It is my understanding that comparing subsequent cells within a field in a database cannot be done- so I thought I'd see if there is a way to go around it.
I have a dataset for pedestrian activity, with over 3 million rows and 40 columns - too big for excel to handle.
I need to sort the entire dataset by 2 fields, following which I need to search down the field containing my pedestrian ids (numbered 1, 2, 3... till approx 10000), and when my ped id changes from one to the next, I need to check the value in a field showing the ped location, and if that matches with the ped's previous location, I need to copy out a cell corresponding to the previous cell's time stamp. If it doesn't match, I need to copy out another time stamp from another field.
Any help would be much appreciated.

Thanks,
Barad..

 

[jdraw]

I suggest you do some research on database design.
Here's a tutorial

Good luck