Please create a new button on Campaign Item Level for checking a exclusive Campaign Items against all other exclusive Line item in the same or overlapping Timeframe fro the same AdPrice.
Name for the Button : Exclusivity Check
in the Background a Batch or something similar will check for that campaign Item is there any contending line Item in Advendio.
Please inform the the user that take a bit time with a Notification after pushing the new button:
On the campaign item object you will find a new button Exclusivity Check which your ADmin can add to your campaign item layout.

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In the background ADvendio will check if for that campaign item any contending line items exist. 

After pushing the button you will get the following notification:
"Exclusivity check started. Please note that the check of Campaign Item may take some more time. The result will be posted in the Chatter Feed of the Campaign Item.”

After finishing the request please create a Chatter notification:

Your Exclusivity check has been finished with following results:
- Campaign Item "{!ciName}" in the Media Campaign "{!mcName}" ({!ciUrl})
- Campaign Item "{!ciName}" in the Media Campaign "{!mcName}" ({!ciUrl})

Please create two new fields to save the information

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If you are using Chatter:

The following notification is created on the campaign item record.

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You can also add two related fields with the following information to your layout:

• Last Exclusivity Check- Timestamp from the last started Exclusivity Check (InlineHelp/Description Indicates which indicates the last time exclusivity has been checked for this line item.)
• Exclusivity Check Status - is there is any contending line item with the status booked please write into the field the number of contending line items with the status booked else OK (InlineHelp/Description:  Shows the status of the last exclusivity check on this line item. Possible options are: OK - no contending Line Item exists / or the number of existing contending line Items.)