One of our products are curtains, we sell them by measure scale like this: 

22"(w) x 22"(h) = $25

26"(w) x 22"(h) = $30

30"(w) x 22"(h) = $35

The list of possible measures for one sigle model of courtain is long with different prices as shown above. The best way to do it would be typing the especific measure we got from the client and the system automatically take the next price in scale. I don´t know if that´s possible, if not, ¿What would be the best way to do it?

Thanks.