Good evening!!!

In my spreadsheet Column A is the "start" date, Column B is the "finish" date and Column C is the difference between the two (in days).

I'm after a formula which'll allow me to calculate the average number of days by month based on Column B (i.e. what is the average number of days for everything with a "finish" date in April, the average number of days for everything with a "finish" date in May etc.).

I've tried using the AVERAGEIF formula but I suspect it isn't compatible with Excel 2003 which I'm forced to use (my job doesn't use anything later).

All suggestions welcome and very much appreciated!!!

Many thanks.

Ed