Refreshing Expression on Form

[aussieolie]

I have written an expression to update a form's details. (quantity x price = total). What i want to do is once i have entered in the price or a particular field, it updates/runs the expression so it works out the total immediatly.
Any suggestions?

Thanks Olie

 

[Idjit]

Key the expression to the price fields "on change" or "after update" event property.