I have the below scenario to achieve :
At the time of saving the Opportunity record, I want to invoke a webservice call to the external system. If the response of the call is greater than some value, then a opportunity record should be created else it should not be created. That is, I want to restrict the creation of the opportunity record based on the response of the webservice call.
As I understand, Salesforce can override only some specific standard buttons like New, View,Edit,Delete. However one cannot override the Save button.
Any suggestions on the approach will be useful.