Count dates based on lookup Criteria

Hello everyone! I've run into a bit of a hold up. I'm trying to count the days of project duration on a table with repeated dates and multiple project numbers.

What I'm looking for is a formula that will look at the date list for a specific WO# (or project id) and return what day number that was. What would also be useful is how to find the start in finished date (the min and max) based on the lookup...but i have a feeling one answer will lead me to the second.

I've attached a simple file to help.
formulating day count.xlsx

Thanks for the help!

Okay, I Figured it out I think...

{=[@DATE]-MIN(IF([WO'#]=[@[WO'#]],[DATE]))}

FDibbins,

Thanks for the help! The @ used in the formula is used in a dynamic table formula. [@Date] points are the "Date" Column for the same row.