Hi Swathi,
I am also struggling with the same probelm,i tried to use your formula but didn't worked.
I have a repeating table which has got a field ISBN.I want to make sure that data entered in ISBN box across repeating tables are not the same.
So,on the datavalidation for the ISBN textbox,i choosed The Expression and copied your formula replaced with my groupname and field name
. = ../preceding-sibling::my:ISBNDetails/CRFH_ISBN1 and . != "" to the text area next to the expression.Now tried to insert same ISBN's bit not message nothing.Can u help me please with this.
Thanks,Adi