This is a problem I've ran into several times, and I imagine that others have ran across it too.
Basically, I have a complicated equation, and I want the user to type in the values needed to calculate the results. (For what it's worth, there are good default values for the variables in the equation.)
I've constructed a GUI that shows the user the names of the variables/fields that need to be provided, along with a control (like a numeric up/down, slider, etc.) to enter the values of the field. Below that, I have an area that shows the output of the equation.
So my question is this. Should my results area automatically change the calculated results whenever the user makes any changes to any of the input fields, or should they push a "Calculate" button to generate the results?
One other thing that probably applies is that the user is not trying to "get the right answer" out of the results. They shouldn't be using the output to then go back and modify the input to get a better answer.
Are there any benefits to requiring the button press? Is the extra click to see the results worth those benefits?