I can't understand what you are describing. Can you describe the design of your table and what your calculation is supposed to calculate?
What is the mathematical connection between an amount of 100 to 300 and fee of $15 to $45? Is this fee supposed to be 15% of the amount?
What does that ave to do with 15 in the Days field?
Set the "Fee" number field to Auto-Enter the Calculation, with "Do not replace existing value" unchecked.
fixed fee is on lookup
its already bringing up calculating for 50 or 25 days from $50, 100, 200, 300 But i have added 150 and 250 also added up fee from Value but it does not bring up automatically for those and works fine for old amounts with 15 or 25 days