If nesting limits

I am looking for a solution to this spread sheet. A little back ground mite help to under stand what I am trying to accomplish is I supply and install Accordion shutters, the shutter widths only come in certain sizes. (see Shutter size chart) and the building openings varies. When I order, I need to go to the next size larger than the window.
The problem is the nesting limit; the size chart contains 70 sizes.

I input the actual opening width in C5 and Excel finds the width size that is the same or the next size lager.
Example
The width is 20, which is between 17.6 &23.5 on the Shutter size chart, I enter that in C5 excel returns the value of 30.25 from line 4 on the Shutter size chart.

So I think should be looking for a equal to or greater than type formula but there are so many arguments