Transact SQL :: Calculate Third Column Using Second Column And Variable

create table #t
(
id int,
col1 decimal(18,2)
)
go

[Code] ...

-- I want to subtract @X and col1. But my variable @X must be reduced for each value in col1 for each next row until it reaches zero.

-- OUTPUT:

-- id col1 col2
--@X at starting point is 15000
-- 1 5000.00 0 --@X IS 10000 = 15000 - 5000(col1)
-- 2 1000.00 0 --@X IS 9000 = 10000 - 1000
-- 3 10000.00 1000.00 --@X IS 1000 = 9000 - 10000
-- 4 12000.00 12000.00
-- 5 300.00 300.00
-- 6 35000.00 35000.00

--in col2 i just put zero where col1 is substract from @X and continue for every subsequent order.
-- in 3 row value is 1000 becouse @X is that big (1000 left from col1)