IsHoliday

To subtract business days from a given date, the following code can be used in a Special Browser script field that will populate a Calculated Value Custom Field with the new date.

In the Special Browser script field you define the function that subtracts the a number of days from a given date

function bus_date_subtract()
{
  var frm=document.forms[0];
 var formatstr="dd/mm/yyyy";
  var start=ConvertDateStr(frm.startdate.value,formatstr);
  var sub=-5;
  for(i=-1;i>sub;i--)
  {
    var cdate=dateadd(start,'D',i);
    if(!isHoliday(cdate))
 sub--;
  }
document.frmevent.cf_1742956 .value=cdate;
}

In Expression section of the Calculated Value Custom Field you would call the function:

bus_date_subtract();

Note: The function definition can be changed to accept parameters (fields containing dates) that are passed at the time of calling the function from any Calculated Value Custom Field.