Estimate new time

I have a ordersystem with repeating orders. Each order has a orderline
with a frequency and a intervaltype (day, week, month and so on) for
indicating how often a task should be done.

When an task/job is done, an equivalent receipt with receiptlines is
generated.

When a new job/task should be suggested, it has to calculate the
shortest next intervallength for each repeating orderline. This
intervallength must then be added to the date of the last receiptline.

I want to to this all in a SPROC. My result should be the one next
orderline that should be carried out with a date for when this is.

RESULT
OrderID TaskID TaskDesct EstDate
5000 GETGROCERIES Pick up groceries for miss Lama 19.12.2003

************************************************************************
Is this possible to do all in a SPROC and not having to do any in .NET
(which this is developed in), and can you help me with some ideas?
************************************************************************

To se my starting point, se the diagram at:
http://www.promotion.no/div/diagram.gif

My mind is stuck and this is so far I've reached:

ALTER PROCEDURE dbo.GetNextOrders
AS
CREATE TABLE #Interval
(
ivID int IDENTITY(1,1),
ivTaskID char(20),
ivTaskDescr nvarchar(200),
ivHour int
)
INSERT INTO #TemporaryTable
SELECT RepID, RepIntName
FROM RepeatInterval
SELECT InvoiceDetails.iID, InvoiceDetails.ReceiptID,
 InvoiceDetails.OrderID, InvoiceDetails.TaskID,
 InvoiceDetails.TaskDescr, InvoiceDetails.DateRegistered
FROM InvoiceDetails LEFT OUTER JOIN
Orders ON InvoiceDetails.OrderID = Orders.OrderID
WHERE (Orders.DateStart < GETDATE()) AND
 (Orders.DateEnd > GETDATE() OR Orders.DateEnd IS NULL)

If you are still struggling with this, could you post some example data and results for each table involved?

Terri|||Thanks, but I think the solution is close at http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=10177