title: Check if value exists in list - View Calendar
body: <p>i created a list and use the view Calendar. Now Need to block duplicates values ​​with the same hours and days..</p>
  
  <p>I would like to use 3 keys( Date Start, Date End and Room of Event ), before the user to insert in the lists i need to check, if that there are this values..</p>
  
  <p>The Calendar of Sharepoint, do it, but is limited..</p>
  
  <p>I've tried to create an indexed field but not solved ..</p>
  
  <p>thank you...</p>