I am showing an exert of a 500 line list below.

B C

917585

3K00300F##

917585

3K00300F##

917587

3K00300F##

917587

3K00300F##



I want to get rid of duplicate 3K numbers but only if it is in the

same serial number. Basically I need to change it to look like:



917585

3K00300F##

917587

3K00300F##





I know I can do this with a loop checking each one individually, but

since my list is 500+ lines (up to 1000) that would take a lot of time

and I want the code to process a bit faster than that. Can anyone

think up a better way?