Compute month wise pending audits

Assume a three column dataset showing Audit ID, Date of receipt of audit mandate and Date of audit completion.  There are other columns as well but they are not important for our Analysis.  One may want to compute the following month wise:

1. Which (Audit ID) are the audits pending at the end of every month; and
2. When (Date of receipt of audit mandate) was the mandate for these pending audits received; and
3. Ageing of these pending audits i.e. this would be computed as the last date of the month less Date of receipt of audit mandate

Here’s an example:

In January 2014, there are a total of 10 audits reports which were received (Filter “Date of receipt of audit mandate” column on January 2014).  Of these 10 audits, 4 were completed in January 2014 (Filter “Date of audit completion” column on January 2014) itself and therefore there are 6 pending audits.  To this figure of 6, we need to add the audits pending from previous months.  If one filters column “Date of receipt of audit mandate” column on Oct-Dec 2013 and “Date of audit completion” column on dates after January 2014, 8 rows will appear.  This means that there are 8 audits which were received before 1 January 2014 but were completed only after 31 January 2014.  So the total number of pending audits as at 31 January 2014 are 8+6=14.  This task needs to be carried out for all months.

You may refer to my solution in this workbook.