I know about the normal formula to calculate the difference between two dates (=(YEAR(A4)-YEAR(A3))*12+MONTH(A4)-MONTH(A3)), however, I'd like a formula that does the same thing but doesn't round up, ie it takes into account the days, and reports back only full months between the two dates.

For example if a child was born on the 26th May 2009, and today is the 25th May 2010, they are not yet 12 months old (1year), they are 11 months old.

Does anyone know the correct formula for this?

Thanks