Trying to return a column header in a cell based on a value

I've searched this and other forums, but haven't found an example of what I'm trying to do here, and you guys were so helpful to me when I borrowed this spreadsheet from its OP that I figured I needed to give you guys another stab at it.

NVBC helped a lot with one formula, but I need to go a step beyond that formula. In this workbook I have highlighted the cell containing the formula I got from NVBC (data!$A$13), as well as the cell it's referencing in the table to the right of it (data!R$8$).

What I'm trying to do here is enter a formula into a cell on the other worksheet (interface!$B$11) that will return the column heading above the value in data!$R$8, which is (3) 2x10. This wil tell me that, based on the formula result of 573, the resulting header or beam thickness will require 3 2x10s.

My hope is that, if someone can help me with this, I can figure out the rest. Then, some day soon, I can pass this spreadsheet around to all my designers and crew foremen and they can use this to cut our time way down.

Header and Beam Calculator.xlsx

That did exactly what I wanted it to.

Thank you, ChemistB.