Simple question

[KenM]

Hi, How do I calculate the difference between the last value in a column and the previous value?

[NTC]

not so simple.

database tables are for storing data...not performing excel style calcs...

there is no such thing as "last" and "previous" in a database table - - they are all just records in a table. Assuming you have a sequencing field then the "previous" record could be determined as current field - 1

maybe easier to do this in the form when data is originally put in

can be done via an advanced sql query that joins the same table on itself - somewhat beyond this forum

can be done via a report - isolate the two records into a query and make a report on them