Window Blinds business question

We acquired the commercial version of the wombat with all plugins, even not needing all at this moment. We are enjoying the setup, very robust solution and very well laid out , however we need help with an issue we couldn’t get solved with both AI help or documentation… unless it is right in front of my eyes… We have the Width and Height working great and calculating correct using the 4 uploaded price grids. We need to have the Fractions for width and Height using the price grids too. When at 0 (default value) there is no change to the cost but when going higher it will have to switch to the next cost on the price grid that corresponds to the change. Ex: have a pulldown menu with 0″, 1/8″, 1/4″ and so on. All of the values should only increase to the next price grid value as the blind will have to be cut to the specified measurement requested by the client, so we must keep the width and height with the original selection but under the hood the system should tell us that the client ordered a 24″ x 36″ 1/8″ where the 36 will be billed at the next height value on the price grid associated to his product. Tried formulas of all types but can’t find a way to accomplish this… should it be by using a variable? How? Any help would be great!