=AND($A1=$A2,$B1=$B2,DATEDIF($C1,$C2,"m")<9)[/QUOTE]
Thank you! Pecoflyer. I changed the $B1=$B2 to $B1="C"
This formula validates birthdates of siblings. We were told that parents and children's bdates in the database should not be less that 8 yrs difference. Who gives birth at 8 yrs old? Horror!!