how to make constant value in MSSQL without cursor

I have one table that I will loop without cursor in MSSQL.

Unit    Speed     C           Count         x      y
A     | 200     | 200       | 3           |   3  | 0
A     | 230     | 230       | 4           |   7  | 0
A     | 240     | 240       | 3           |  10  | 0
A     | 250     | 255       | 2           | >=12 | 5
A     | 260     | 255       | 2           |   2  | 0
A     | 270     | 255       | 2           |   4  | 0
A     | 280     | 255       | 3           |   7  | 0
A     | 290     | 255       | 4           |   11 | 0
A     | 300     | 260       | 2           | >=12 | 5
A     | 310     | 260       | 2           |   2  | 0
A     | 320     | 260       | 2           |   4  | 0
A     | 340     | 260       | 2           |   6  | 0

How to make C value is constant (speed + 5 for first record and C + 5 for next value) after summary of X value is equal or same with 12?

I want to loop the record without cursor (because if I use cursor, database will be deadlocked).

Solution

With a little help from common table expressions and some window functions I came up with the following solution. Note that you need some column to sort the table.

With cte AS 
(
SELECT RowOrder
      ,cCount
      ,SUM(cCount) OVER(order by RowOrder) As SumcCount

FROM Tbl
)

SELECT RowOrder
      ,cCount
      ,SumcCount % 12 as x
      ,CASE WHEN SumcCount >= 12 
       AND RANK() OVER (Partition by SumcCount / 12 ORDER BY RowOrder) = 1 THEN
           5
       ELSE
           0
       END As y   
FROM CTE
ORDER BY RowOrder

Explanations:

Common table expressions is a way to create temporary result sets.
using the SUM function with the OVER clause allows for cumulative sums on cCount (i didn't want to use count since it's a reserved word).
using the RANK function gave me a simple way to determine if the cumulative sum of cCount equals to any multiplication of 12 or more. note that in the case there is also a condition that the cumulative sum of cCount is 12 or more.