FileMaker Pro Custom Functions

/* //PostPer_Day ( Post; startDate ; finishDate ; returnType ) PostPer_Day Post startDate finishDate returnType */ Posts / Let( [ availableDates = Case ( not IsEmpty(startDate) and IsValid(startDate) and not IsEmpty (finishDate) and IsValid(finishDate) ; "both" ; not IsEmpty(startDate) and IsValid(startDate) and IsEmpty (finishDate) ; "start" ; "none" ) ; days = Case ( availableDates = "both" ; GetAsDate(finishDate) - GetAsDate(startDate) ; availableDates = "start" ; Get(CurrentDate) - GetAsDate(startDate ) ) ; months = Round ( days/30 ; 0 ) ; years = Round ( days/365.25 ; 0 ) ] ; Case ( returnType = "d" ; days ; returnType = "m" ; months ; returnType = "y" ; years ) ) /* Calculate the number of days "d", months "m" or years "y" between two dates With the help of on of Michael Richards functions*/
 Then copy & paste into FileMaker Advanced's Edit Custom Function window.