In order to avoid overbooking it is possible to disable the use of the Media Search altogether by giving the Sales User only the option to add items through the Booking Calendar. You can create a new custom button for the Media Campaign to enter the Media Configuration using the baskets. Here is how you do this.
- Open the object Media Campaign (Setup - Create - Objects - Media Campaign)
- Scroll down to Buttons, Links, Actions
- Click on New
URL-button: /apex/advendio__mediaconfiguration?id={!ADvendio__MediaCampaign__c.Id}&modifyCiType=Campaign+Item+Creation&useBaskets=true
Now add this button to the layout. It will lead the user straight to the Media Configuration.