I have to build two solutions that require calculations in a record that are evaluated based on values in the preceeding record. For instance, one solution is a training log where an individual's performance on a particular exercise is tracked. As the individual increases the amount of weight being used in the exercise, another field displays the percentage improvement over the previous recorded amount.

In another solution, I am recording a series of odometer readings. Each record has a reading but it also has a field that displays the difference in mileage between each odometer reading.

I'm lost and was hoping that someone could give me an example of how to make this work.

One way is to preserve the previous value in a separate field in the new record. Another way is to store the previous record's ID in the new record, and relate to the previous record with a self-join.

What about using a calculation that uses the "lookupnext" function? Any examples?