Below is an example of what I think you are trying to do. This proc will keep calling itself until it's done. I am using an arbitrary surrogate key to break the job into batches; the proc will execute (<#of rows to update> /@row_end) times.

Here is some sample data:

-- (1) Let's create some sample data

USE tempdb

GO

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

CREATE TABLE #sometable(some_id int primary key, some_value varchar(40), some_date date);

WITH iTally(n) AS

(SELECT TOP 100000 ROW_NUMBER() OVER (ORDER BY (SELECT (0)))

FROM sys.all_columns a CROSS JOIN sys.all_columns b)

INSERT INTO #sometable

SELECT n, 'old value', getdate()-(2500+floor(2500 * RAND(convert(varbinary, newid()))))

FROM iTally

GO

--BEFORE

SELECT * FROM #sometable

ORDER BY some_id

GO

Here is a recursive stored proc with a couple examples:

-- (2) The recursive update stored proc

CREATE PROC someproc(@row_start int=0, @row_end int=10000, @new_value varchar(100)='new value')

AS

SET NOCOUNT ON;

WITH surrogate(s_key) AS

(SELECT ROW_NUMBER() OVER (ORDER BY some_id)

FROM #sometable)

UPDATE #sometable

SET some_value=@new_value

WHERE some_id>@row_start AND some_id<=@row_start+@row_end;

SELECT @row_start=@row_start+@row_end;

IF @row_start<(SELECT COUNT(*) FROM #sometable)

EXEC someproc @row_start,@row_end,@new_value;

GO

--using the defaults

EXEC someproc

--50,000 rows

EXEC someproc 0,50000,'blah, blah'

Perhaps this will help.

P.S. I came up with this in a few minutes during lunch and don't don't know if this is the best way to accomplish this or not (comments, criticism welcome).

EDIT: my stored proc had a couple issues. All fixed.