Lifing Chart

[mmotorsport]

trying to develop a chart to keep track of car parts. I have included a portion of the sheet I'm trying to make. engine2 is the sheet I am making. Engine is the sheet I'm starting with, which I did not make. I want it to be so if I put an x in the column it will select the part used and then add up mileage for the events where there was an x. As soon as I go to a different row I get a data error and I'm not sure why. Also in sheet Engine2 all the formulas show when I hit show formulas, where as Engine shows the formula in the data bar, but only shows up on "show formulas" when data is entered in the cell.

I thought I have the formulas entered the same .

Sorry if the description is long winded

PLEASE HELP and thankyou all in advance for your assistance