Looping through a table

I have table1 with fields KEY1, KEY2, QNTY
rows :
1234, 1, 1000
1234,2,2000
1235,1,4000
1235,2,5000
1235,5,6000
KEY1+KEY2 will be unique in this table
I have table2 with fields KEY1, KEY2, SDATE, SQNTY
Rows:
1234,1,A,500
1234,1,B,500
1234,1,C,500

1234,2,A,1000
1234,2,Q,1000
1234,2,Z,1000

1235,1,A,2500
1235,1,B,2500
1235,1,G,2500

1235,2,S,5000

1235,5,D,4000
1235,5,D,4000

The totals of SQNTY for KEY1+KEY2 in Table2 are shown as more than the corresponding QNTY of KEY1+KEY2 in Table1

I want to skip through Table1, and pick out rows from Table2 matched over KEY1+KEY2 which is ordered by KEY1+KEY2+SDATE(desc) till the sum of SQNTY is greater or equal to QNTY in Table1. If the sum is greater, the SQNTY for the last row is re ...