Is there any way, when using the system defined buttons in Books/CRM finance. To halt the creation of a sales order if a sales order has already been created? 

We are having issues with our staff creating duplicate sales orders in the system. 

We have had a solution created that works via a custom field or custom button. But there is no way to disable the system defined convert buttons, so then even if we do implement these controls, there is no fool proof way of ensuring that they do not use the system defined button. 

Thanks in advance, 

Eoin