Excel 2007 : Calculating Percentages

See Sheet1

If this is okay, then what I did was clicked a cell in column A, then go to Data|Pivot Table and Pivot Charts..

Click Next

Ensure Range includes title of column in A13 and the full column A range.

Click Next,

Click Layout,

Drag the Error button from the right to the Row area and then drag it again to the Data area... double click on the Count of Error button in the Data Area... Click Options and click in the Show data as drop down and select % of column.

Click Ok.

Click Finish.