Summing and Averageing, based on criteria.

Hi All,

I currently have an excel table with staff members names (which wont change) and I'm seeking a way to work out the average time it takes them to complete a project.

Project1a.xlsx

In this example John and Mike both have projects catogorised in 2 types, A and B. I'm after a way that will calculate the difference between all of the review dates and all of the start dates for John and Mike for Type A and Type B projects, and give me an average of this. Then I would like the same to happen between Review date and Completed Date.

If this needs to be explaing further please let me know, any help will be greatly appreciated.

Thanks!