I would say the new Calculation modes but it looks like these are not supported in the web yet.
Are you talking about this URL param?
Recalculate values when in edit mode (forceRecalculate)
Use the forceRecalculate URL parameter to force certain fields to be recalculated, even if the record is opened in edit mode. This can be very handy, for example, if you want to record the name of the person editing the record, or to refresh the date when the record was last edited.
If so post the URL you are trying so we can try and fix it.
You can also use an if(the field they change, value, value) to trick it to fire. I have even seen a did you change something question that you then use in the if to get it to recalc.