Formula for days counting

Hi

I have two sets of data. The first one is Accounting Year End of each firms, and the second set of data is Trading days of each firms (assigned as 0 or 1). My aim is to count the number of trading days in each accounting year of each firm. I use Code as the key factor to link two sets of data.

I struggle to link two files because,
1) accounting year ended of each firm can be changed
2) the first file, accounting year end, is annual data; whereas the second file is daily data.

For example,Firm 26360V, its year ended for 2005, my counting will cover 30/09/04 to 30/09/05. There is no counting for 2006. Then, for year 2007, my counting will cover 31/03/06-31/03/07 (however, there' is the date 30/03/07 but no 31/03/07 because it is the weekend)

How can I create the formula. I also attach the example file

Thank you very much for your help.