Excel 2007 : Creating a calculated item in a PivotTable

Hi all,

I just started using PivotTables, and I'm having trouble making a calculated item. I'm using the PivotTable to keep track of participant data for a study I'm running, and I want to use the number of "hit" and "incorrect" responses to calculate their accuracy on a task.

I currently have it organized like so (range of values in parentheses):
Column labels: Block (1-4)
Row labels: Condition 1 (condition A or condition B), Subject ID, Condition 2 (condition C or condition D), Hit/Miss (hit, incorrect, or miss)
Values: Count of Hit/Miss

I've been trying to make a calculated item by first clicking on one of the row headers, going to the Options tab, clicking Formulas, then selecting "Calculated Item...". When I do that, I get an error message that reads: "If you're trying to add a calculated item, you cannot do so because a field has been used more than once, either in the data area two or more times, or in the data area and another area at the same time. Change the PivotTable report so that no field is used more than once, and then try the calculated item command again."

Can anybody help me understand what this means? What is the data area as opposed to other areas, and what would it mean to use a field more than once?

I have tried making a new PivotTable using a single column from my raw data sheet, and I've been getting the same error. I've also tried clicking in other areas of the table before trying to calculate the item, and nothing is working.

Thanks in advance for your help!

Why not upload a sample file, to help in your query ? It sounds as if you are not clicking in the pivot field before going to the calculated field option.( you can click in any field) Also if you upload an example, put in your expected results, calculation etc