D'oh! forgot to add the very first query that needs to be run:

SELECT Min([dt]) AS MinDt, Max([dt]) AS MaxDt, DateDiff("m",[mindt],
[maxdt]) AS MaxMths, MonthsBetweenDates([MinDt],[Maxmths]) AS MthsBtwn
FROM Table1
WHERE (((Table1.dt)#5/1/2011#));

:-)