There comes a time in many Excel users' careers where we start to write incredibly complex Excel formulas to summarise or extract data from poorly structured workbooks.
The true Excel Guru knows that if the data were in a tabular format we'd be able to use the amazing tools Excel has available. Tools that make mincemeat of complex formulas.
So, next time you're faced with a complicated formula you should ask yourself if changing the layout of the workbook could be the solution instead of writing a mind bending formula that is likely to end up broken the minute a less experienced Excel user tries to edit it.
Full article: Avoid writing complex Excel formulas