Do you want to block unnecessary impressions made by a user,which results in un-fair payment?
Frequency Capping Mod will helps you to overcome this problem.
This mod allows you to set time limit and number of times a user can able to make impression on same banner.
If impressions made by a user surpasses the specified number within specified time period,then openx will not log further impressions.
Openx will continues to log impressions only after the specified time limit is met.
To purchase this product, you can go to this link and place the order.