how to compare if multiple cells are equal

Hi All

I need to compare the data in three fields and if the same ignore but if different then add them with a space and a hyphen.

I use this formula for 2 fields and it works great I just can't get it to work with three.

=IF(TRIM(Data!BC2)=TRIM(Data!AY2),TRIM(Data!BC2),TRIM(Data!BC2)&" - "&TRIM(Data!AY2))

I use the trim command as the users entering data often add unnecessary spaces etc. and it combines the data even when the same.

Any help appreciated.