Rolling 12 month sum multi dimensional pivot table

[phoenix]

have these two tables:

LINE_ITEMS1:
Load * Inline [
Account, grade, range
1, A, 10-20
2, A, 20-30
3, A, 10-20
4, B, 30-40
5, B, 30-40
];

LINE_ITEMS2:
LOAD * Inline [
Month, Account, loss
1, 1, 0
2, 1, 0
3, 1, 0
4, 1, 100
5, 1, 0
1, 2, 0
2, 2, 0
3, 2, 0
4, 2, 0
5, 2, 0
6, 2, 0
7, 2, 0
8, 2, 0
9, 2, 0
10, 2, 22
11, 2, 0
12, 2, 0
1, 3, 0
2, 3, 0
3, 3, 0
4, 3, 0
5, 3, 0
6, 3, 0
7, 3, 0
8, 3, 0
9, 3, 0
10, 3, 50
11, 3, 0
12, 3, 0
1, 4, 0
2, 4, 0
3, 4, 0
4, 4, 0
5, 4, 0
6, 4, 0
7, 4, 0
8, 4, 0
9, 4, 0
10, 4, 11
11, 4, 0
12, 4, 0
1, 5, 0
2, 5, 0
3, 5, 0
4, 5, 0
5, 5, 0
6, 5, 0
7, 5, 0
8, 5, 0
9, 5, 0
10, 5, 200
11, 5, 0
12, 5, 0

];

I want to calculate rolling 12 month loss for each grade and range combination at each month.

desired result:

Month	grade	range	rolling_12_loss
1	A	10-20	0
1	A	20-30	0
1	B	30-40	0
2	A	10-20	0
2	A	20-30	0
2	B	30-40	0
3	A	10-20	0
3	A	20-30	0
3	B	30-40	0
4	A	10-20	100
4	A	20-30	0
4	B	30-40	0
5	A	10-20	0
5	A	20-30	0
5	B	30-40	0
6	A	10-20	0
6	A	20-30	0
6	B	30-40	0
7	A	10-20	0
7	A	20-30	0
7	B	30-40	0
8	A	10-20	0
8	A	20-30	0
8	B	30-40	0
9	A	10-20	0
9	A	20-30	0
9	B	30-40	0
10	A	10-20	150
10	A	20-30	22
10	B	30-40	211
11	A	10-20	150
11	A	20-30	22
11	B	30-40	211
12	A	10-20	150
12	A	20-30	22
12	B	30-40	211

any suggestions?

hanks