Adding business days to a date via MagicETL

Hi, I'm currently calculating a deadline using a dynamic formula in MagicETL. It looks like this:

CASE WHEN `issue` = 'bug' THEN (
     WHEN `priority` = 1 THEN ADDDATE(`CreationDate`, INTERVAL 4 DAY)

The calculation works great, but I was wondering what would be the best way to update it to 4 business days, rather than calendar days (as interval uses)? I was reading the documentation here but it only covers calculating business days between two dates, rather than adding business days to a date.

I also looked at the available date operations available in MagicETL and see that there is a "Add To Date" option but unfortunately "Business Days" is not a unit of measurements - which would be really useful.

Any ideas on how the above case statement could be modified to use business days instead? Thanks!