Is there a set formula or calculation that is used to determine the price based on these values or do you need to look it up based on the values? If you need to look it up this might require a table in your db. Either way you would have the user select the height and width then add the item to your cart. You would then either have a calculation that will determine the price based on the options selected and added to the cart. The other way would be to have a table with the values that you can query based on the user inputs. Then just bind the value from that rs to the price column in your cart.
I think that the easiest way to do this would be to create a table in your db that contains all of the information that would needed to be looked up in the list. You can start with one height, and the first width, then the next record would be the same height with the next width. When you finish with one height you can go to the next.
In the end this would give you a table with all of the possible width, height combinations stored in individual records.
Once the table is ready you can then have the user make a selection for the width and height and add the item to your cart. You would then need to have a recordset on the page that will select the records from this table and filter based on the values the user selected. The final part would be to bind the price from this recordset to the price column in your add to cart server behavior.
Getting the prices based on the options like this is not a feature of eCart but doing it this way you should be able to get the price dependent on the user selections. Let me know if you have any questions about any part of this and I would be glad to help advise you on it.