Measuring Consecutive Years

Hi there.

I work for a charitable organization, am new to this form (and sql programming) and trying to create a flag for unique records indicating the number of consecutive years a donor has given.

I have create a sample db idenifying donor, giving year and total pledges with multiple donor records existing for multiple years having donated.

CREATE TABLE mygifts06 (Donor_id varchar (10), Gift_yr nvarchar (4), Tot_pledges numeric (16,2))

INSERT INTO mygifts06 (Id,Gift_yr,Pledges)
SELECT 155758,2005,15.00 UNION ALL
SELECT 155759,2004,25.00 UNION ALL
SELECT 155758,2004,40.00 UNION ALL
SELECT 155757,2005,100.00 UNION ALL
SELECT 155758,2002,30.00 UNION ALL
SELECT 155758,2001,120.00 UNION ALL
SELECT 155755,2003,15.00 UNION ALL
SELECT 155758,2006,80.00 UNION ALL
SELECT 155757,2003,65.00 UNION ALL
SELECT 155759,2005,400.00


For the above dataset, I am trying to create the following output

Donor_id 2_consec_gifts 3_consec_gifts 4 consec_gifts
--------- -------------- -------------- --------------
155755000
155757000
155758110
155759100


Do I need to use a cursor for this task? I lack experienced in using cursors is there an alternative method someone could suggest?

Thanks in advance.