how to change color of a field if it is duplicate..........

hi guys
how can i change the fore color of a field value if there is a duplicate of it.
thanks in advance but only for those who help me (Lolz) ;)
Sillytry like
in format editor in the font tab write a formula on color [x+2]

IF (field1) = PREVIOUS(field1) THEN
RGB(255,0,0)
ELSE
RGB(0,0,0)

Gragi|||hi grag

thanks for ur reply but problem in my case is that
the duplicate value can reside any where in the list.