Add Variable to Created Variable, If Then Else

[mattmm]

Have: Data ordered by unique Code, by unique ID, with static Date1 and static Item1.

Code1	Date1	Item1	Id
1	2/23/21	5	1
1	2/23/21	9	2
1	2/23/21	6	3
2	2/23/21	7	1
2	2/23/21	3	2
3	2/23/21	4	1

Want:  When ID eq 1 then Want1= Item1 + Date1, else add Item1 to Want1 while retaining the value of the previous Want1 until the end of the ID of Code1.

Code1	Date1	Item1	Id	Want1
1	2/23/21	5	1	2/28/21
1	2/23/21	9	2	3/9/21
1	2/23/21	6	3	3/15/21
2	2/23/21	7	1	3/2/21
2	2/23/21	3	2	3/5/21
3	2/23/21	4	1	2/27/21

Code1	Date1	Item1	Id	Want1
1	2/23/21	5	1	2/28/21
1	2/23/21	9	2	3/9/21
1	2/23/21	6	3	3/15/21
2	2/23/21	7	1	3/2/21
2	2/23/21	3	2	3/5/21
3	2/23/21	4	1	2/27/21

I have experimented with the code below but I'm unsure how to keep the created value of want1 when id =1, and then add item1 when id ne 1 by code1. Any thoughts or help is greatly appreciated.

data want; set have;
by code1 date1 id;
if first.id then want1 = item1+date1;
           else ?
run;

[mattmm]

I figured it out by utilizing retain. 

data want; set have;
by code1 date1 id;
retain want1;
if id=1 then want1=date1+item1;
else want1= want1+ item1;
run;