A custom CRM validation rule is created against the Call2_vod__c object. When a user violates the rule, an error message displays multiple times.
Validation rules run for all Call2_vod__c records being generated, both parent and child. This can also happen against Event Calls and Group Calls.
Validation rules can be updated to only consider parent calls. For example, ISBLANK(Parent_Call_vod__c) = YES indicates a call is a parent call.
CRM Help: Offline Validation Rules: Call Reporting Considerations