Varying Formula based on Size

[mgm213]

I want to write a formula that will pull the size from Column C and that match a formula that it will be put into one of two columns based on if its Floor or a Cieling Margin. So basically I would insert some sort of VLOOKUP based formula in column D that would pull the formula from P and use the cost in the corresponding I column. Then do the same thing for column E as well.

 

[yearnintolearn]

From that data sheet, as more of clarification, could you input 1/2 values into columns F & G so as to trace the steps a bit better? Thanks