I love the way Probability is calculated from Stage of the Opportunity object.

But how it's done? How can I implement such functionality in my apps?

I've read a about formulas, triggers, apex classes and workflows but they all seem to miss the target because they don't work before "save" button is pressed. Is the visualforce the way to go? Standard Opportunity page doesn't seem to be visualforce.

I love the way Probability is calculated from Stage of the Opportunity object.

But how it's done? How can I implement such functionality in my apps?

I've read a about formulas, triggers, apex classes and workflows but they all seem to miss the target because they don't work before "save" button is pressed. Is the visualforce the way to go? Standard Opportunity page doesn't seem to be visualforce.