Duplicate in one column&unmatching data urgen

hi everyone

hope someone can help me on this urgent matter

I'm able to locate duplicates when I'm putting =a1&b1&c1 and then the if countif

but my problem is that I want to filter my duplicates with an extra condition:

I want only the duplicate if in one column the data is not matching the other
because now i'm getting duplicate in all the columns even though i'm not selecting them with the & in the first formula

so basicLy i need to get

a 300
a 300
a 600

so i need to get only
a 300
a 600

by a formula instead of doing remove duplicates because if i do so my other values will get lost in the other columns.


thanks