"Dip" wrote...
....
Column A, B, C and D could have values C, R, U and D respectively. I
only need to restore unique combination while I am concatinating. In
other words, if the result is "CCRD", then I only want "CRD".
How do i do it?

E2:
=A2&IF(A2=B2,"",B2)&IF(COUNTIF(A2:B2,C2),"",C2)&IF (COUNTIF(A2:C2,D2),"",D2)