I have a custom object
O__c it has Lookup relationship to Opportunity. This Custom Object record will create when oppty stage is moved from 95% to 100% according to our requirement.
Now my question is I have 300 Opportunities already existing which has
O__c Object record Each.
There is a custom field in my custom object and every time when I add new record it should validate me such a way that the recent record's custom field should be equal to it's earlier records. How can I do that?