This is the last working day of the current week:

–––
var myDay := today();
let myWeek := week(today());
while week(myDay) = myWeek do 
   myDay := myDay + 1
end;
myDay - 3
–––

Birger

Or this: date(year(today()), month(today()), day(today()) - weekday(today()) + 4)

weekday(Date) will be 0 for Monday to 6 for Sunday

I like to say that I often walk around the block to go next door...   There may be an easier way.. but this will calculate an end date given a start date and a DURATION in workdays .. it ignores holidays..  If you want to make it EFFORT based.. See the Use Case about calculating workdays accounting for holidays.. 

let d := 7 - weekday('Start Date');
let t := DURATION - d;
let w := floor(t / 5);
let r := t - 5 * w;
let o := d + w * 7 + r + 1;
date(year('Start Date'), month('Start Date'), day('Start Date') + o)

Well.. I guess if it was 

let d := 6 - weekday('Start Date') .. 

I would not have to add 1 back at the end.. :)