Runtime error on adding working days to current date

is fromDate passed as a string?  If so, you can't call the setDate method.  You need to convert the string to a date time and then user associated methods.

For that matter, there is built in functionality in test complete for manipulating dates.  Try the following.

function addWorkDaysToDate(fromDateString, days){
    var fromDate = aqConvert.StrToDate(fromDateString);
    var count = 0;
    while (count < days){
        fromDate = aqDateTime.AddDays(fromDate, 1);
        if ((aqDateTime.GetDayOfWeek(fromDate) !=1) && (aqDateTime.GetDayOfWeek(fromDate) != 7)){

        count++
        }
    }

    return aqConvert.DateTimetoStr(fromDate);
}