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Using the Rule Engine, you can modify target CPA and Target ROAS at the campaign level for your Microsoft Ads account(s).
Setting a Condition
To get started you first need to create a condition to be met. This one could be, for example, to consider all the events where the Impressions for the campaign are more than 200 in the last 240 days, and the Target ROAS (at the campaign level) is <100.
You can read more about how conditions work in the Rule Engine here.
Defining the Action
With this condition set, you can now define an action. Here you can say that if the above condition is met, then the system should, for example, modify the Target ROAS to increase it by 10%, as seen on the screenshot below.
You can read more about how actions work in the Rule Engine here.
Once you've defined the condition(s) and action(s), you can go ahead and press "View Suggestions" to see the results and apply the actions of modifying the values.
You can read more about the suggestions preview page here.