Dennis @ PerfectForms
When the order value field changes data, use a Multiple Branch object. Place 7 Set Field objects arrayed below it (setting the discount amount values). Make a join path from the Multiple Branch to each Set Field. On the join paths create your conditions in formulas (Order amount is equal or greater than 100,00 AND order amount is equal or less than 199,99 – etc…). Each join path will be different. The seventh join path should be always if no other condition is met. On that one maybe you set the discount amount to 0, or maybe you show a message to say the value is out of range.