I have a table that i wouldlike to use for working out area sizes and the appropriate machine to use according to the results. What i have done is set it so that you input the Height (in C3), Width (in E3) and length in (G3). This will then give you the m³ value in I3. This is then multiplied by 10 to give the amount of air changes required for an area of the resulting size in I4. What i would now like to be able to do is input a formula based upon I4's total that divides it by each of the cmh totals (850, 2295 and 5850) and works out the least amount of NPU's required. So if the total in I4 is 1000 then the results would by 1 No 1500, or if the results was 700 then it would be 1 No 500 etc....Once the calculation has worked out what NPU requirement it is it i would like it to show the quantity required in G5 and the type of NPU in I5. If the result in I4 is say 26,000 the it will need to work out the lowest selection of NPU's that total so it would be 4 x 4000 & 1 x 1500.