Excel formula question

[alexlighting]

I have a problem that needs solving. I am making a spreadsheet that consists of 4 sheets. Each of the first 3 sheets' data contributes to the 4th sheet, which is a "grand total" sheet.

Essentially, Our company does inventory, and I input the results of the inventory into the appropriate sheet. Our inventory schedule is broken up into trimesters, so, one sheet per trimester, and then the year-to-date (or, "grand total") totals. The problem is that if the first trimester is 100% completed at 100% accuracy, and the second trimester is 10% completed at 50% accuracy, the year-to-date total would be 75%, instead of somewhere in the 90's. There is a column for completion % and a column for accuracy %. I need to, somehow, have the completion column factor into the accuracy column, thus making our year-to-date column accurate.

Unfortunately, I'm just not smart enough to figure it out.

Thanks for your help!

[tuph]

It would be easier to find a solution if you could zip and attach a sample of your workbook.

[alexlighting]

Here you go.