Lookup & afterInsertMethodName

With afterInsertMethodName we can define a method that the framework call after it has inserted the selected code in the field defined in the fieldkey parameter.
But, if i make some controls in the called method and i need to cancel the insert of the selected data, because not correct, is it possible ? Can i return false and tell to the lookup that i don’t want that value is returned and i want the previous value ?

Thanks