SQL CURSOR Help

Hi.  I am trying to create my first cursor that goes through a table row by row calculating a column called MM_CUM.  I keep track of the previous row's r1_mmestwireless value as it is used in the next row's calculation for MM_CUM.  I try this and it goes through all 15,000 rows and places the same value in the MM_CUM column.  Any help with this would be much appreciated.  Thank you!


DECLARE @iRowId int,
      @r1_mmestwireless money,
      @last_mm_cum money,
      @mm_cum money

DECLARE MarketModel CURSOR LOCAL
FORWARD_ONLY
FOR
SELECT r1_mmestwireless,mm_cum
FROM mm_mal_test

SET @iRowID = 1

OPEN MarketModel

FETCH NEXT FROM MarketModel
INTO @r1_mmestwireless, @mm_cum
WHILE @@FETCH_STATUS = 0

BEGIN

IF (@iRowID = 1)
BEGIN
UPDATE MM_MAL_TEST
SET mm_cum = @r1_mmestwireless
SET @last_mm_cum = @r1_mmestwireless
END

IF (@iRowID > 1)
BEGIN
UPDATE MM_MAL_TEST
SET mm_cum = @last_mm_cum + @r1_mmestwireless
SET @last_mm_cum = @last_mm_cum + @r1_mmestwireless
END

FETCH NEXT FROM MarketModel
INTO @r1_mmestwireless, @mm_cum

set @iRowID = @iRowID + 1

END

CLOSE MarketModel
DEALLOCATE MarketModel
RETURN