Okay, thanks for posting that. A Change event like the Change event where you put your calculation occurs every time something is typed in that textbox, so if for example someone typed 100 in that textbox the calculation would try to run 3 times. You probably don't want that to happen so the best thing would probably be to create a command button and put the code there. Before you do that however you need to think about where the value for far1 comes from.