FileMaker Pro Custom Functions

Let ( [ // determine the typical week-offset in [week 5] of the year [yearNR] . . . $checkdate = GetAsDate (Date (1 ; 1 ; yearNR) + (7 * 5 ) ) ; $checkweek = WeekOfYearFiscal ($checkdate ; 2) ; $wkoffset = 5 - $checkweek ; //make sure that we stay away from week 52/53 in correctional-data; we keep the remaining 21 days in a var $saveweekNR = Case (weekNR > 50 ; weekNR - 3 ; weekNR ) ; $reservedays = Case ( weekNR > 50 ; 21 ; 0 ) ; //first leap to the aproximate date as a basic startpoint, find the right offset for the day-nr. $leapdate = GetAsDate (Date ( 1 ; 1; yearNR) + (7 * ($saveweekNR-$wkoffset) ) ) ; $dayoffset = DayOfWeek ($leapdate) - dayNR ; //maandag = 2 ... vrijdag = 6 //First try (FT) to get close to a plausible date on the right day-nr.: $FTdate = GetAsDate ($leapdate-$dayoffset) ; $FTweek = WeekOfYearFiscal ($FTdate ; 2) ; // Second Correction (SC) with a plausible date, offset is in days (weekoffset x 7) $SCoffset = ($saveweekNR - $FTweek) * 7 ] ; GetAsDate ($FTdate + $SCoffset + $reservedays) // $reservedays :: if we put 2 week aside to stay away from week 52/53 we need to put them back here ! )
 Then copy & paste into FileMaker Advanced's Edit Custom Function window.