To exclude weekends, there is a 'simple' solution doing some simple 'date'math. This has been solved before on these forums...
To also exclude holidays is a lot trickier. The only 'easy' solution I can see is to build a table that holds all dates that should be excluded.
The statement would be something like
CREATE TABLE NonBusinessDays
(NBDDate smalldatetime)
GO
SELECT datediff(day, @creation_date, getdate()) - count(*) AS Outstanding
FROM NonBusinessDays
WHERE NBDDate >= @creation_date and NBDDate < getdate()
Either join to your source table or pass in Creation_date as a parameter.