Finding and eliminating dulicates in the same cell

[outofgum]

The wording of this question was very unclear.

I think the question is not too hard, and will repost a rewritten question in the newbie section.

[martindwilson]

if its only one semi colon as separator in any cell
=IF(LEFT(A1,FIND(";",A1)-1)=MID(A1,FIND(";",A1)+1,255),LEFT(A1,FIND(";",A1)-1),A1)
if its possible cell wont have a semicolon
=IF(ISNUMBER(FIND(";",A1)),IF(LEFT(A1,FIND(";",A1)-1)=MID(A1,FIND(";",A1)+1,255),LEFT(A1,FIND(";",A1)-1),A1),A1)