Looks like it's time for a quirky update solution:

IF OBJECT_ID('tempdb..#temp') IS NOT NULL DROP TABLE #temp;

-- This primary key is crucial. If your table doesn't have a clustered index

-- on this, then you will have to dump the data to a temp table (along with

-- the PK columns of the table), use this PK, then update the real table

-- by joining this temp table back to the real table by the PK columns.

CREATE TABLE #temp (ckid INT PRIMARY KEY CLUSTERED, stat varchar(10), Grp int);

INSERT INTO #temp (ckid, stat)

SELECT 101 ,'Open' UNION ALL

SELECT 102 ,'Open' UNION ALL

SELECT 103 ,'Open' UNION ALL

SELECT 104 ,'Void' UNION ALL

SELECT 105 ,'Void' UNION ALL

SELECT 106 ,'Open' UNION ALL

SELECT 107 ,'Open' UNION ALL

SELECT 108 ,'Open' UNION ALL

SELECT 109 ,'Void' UNION ALL

SELECT 110 ,'Open';

-- declare and initialize variables needed in the update statement.

DECLARE @Sequence int, -- for safety check

@stat varchar(10), -- to hold stat column from last row

@grp int, -- current grp number

@ckid int; -- for anchor column

SET @Sequence = 1;

SET @grp = 1;

/*

This form of the UPDATE statement has some rules for proper usage.

See Jeff Moden's article at http://www.sqlservercentral.com/articles/T-SQL/68467/

for a complete discussion of how this works, and all of the rules for utilizing it.

If you don't follow ALL the rules, you WILL mess up your data.

*/

WITH SafeTable AS

(

-- generate table with a sequence column in clustered index order

-- in order to verify that update is happening in the correct order

SELECT ckid,

stat,

grp,

Sequence = ROW_NUMBER() OVER (ORDER BY ckid)

FROM #temp

)

UPDATE t

-- verify in proper sequence order; if not, throw an error so nothing is updated

SET @grp = grp = CASE WHEN Sequence = @Sequence THEN

CASE WHEN stat <> @Stat THEN @grp + 1

-- if you have to separate this by account numbers also, then you will need

-- a when clause to handle it here also.

-- different stat --> increment grp number

ELSE @grp END -- same stat --> same grp number

ELSE 1/0 END, -- not in proper sequence order, so throw an error

@Sequence = @Sequence + 1,

@stat = stat, -- get the current value to compare to in next row

@ckid = ckid -- anchor column

FROM SafeTable t WITH (TABLOCKX) -- lock table

OPTION (MAXDOP 1); -- prevent parallelism!

select * from #temp;