Stock Rotation Problem

[#1]

I have a table that gives stock Amount for each chossen periodedate, for each item .

and i have to go back to previous sales to see how many days i needs so my sales will be greater or equal to stock.

ex: item= 27, date =01/04/11 (Amount=1000)

if i have sales like that:

Item    Sales    Date

27       200       01/03/11(MM/DD/YY)

27       300       01/02/11

27       550       01/01/11

27       400       30/12/10

number of days so my sales will be equal or greater then my stock will be 3 days.

I always go back to less than selcted date in sales and i count days until i reach the stock amount.

Can anyone help?

this is urgent since i m in middle of a sib session....

[#2]

Hope this helps.

Regards,

Kiran.