Forgot to mention that adding a calculated column to the dataset might be the way to go, but not good enough to get the back end to calculate the field as it needs to be accurate for newly-entered rows that haven't been saved yet.

Of course a "total" field like this is only an example: I can foresee lots of uses for derived fields.

Also one alternative for grid columns would be to override the CellFormatting event, and calculate on the fly, but this seems really kludgey. Using a calculated property like this is so elegant, just doesn't work.