Incidentally, this is what you get with your sample data:

A B
3179 03011979
30179 03011979
52165 05211965
12523 check
030179 03011979
311979 03011979
052165 05211965
120523 12051923
112180 11211980
3011979 03011979
5211965 05211965
1251923 check
03011979 03011979
05211965 05211965
12051923 12051923
11211980 11211980

Pete