Testing a DAX measure using Excel functionality - XIRR example

Power Pivot's DAX is missing many of the Excel functions we've come to take for granted, but it's often possible to simulate them using pure DAX, see here for my attempt at a DAX Percentile function. Even if the logic behind such attempts is sound (or not), the result is likely to be judged against Excel's version. Also, in many cases, due to the limitations of DAX, crafting an acceptable solution may not be possible. The attached workbook shows a method to either test, or replace, such a DAX measure using existing Excel functionality.