Create Two Data Alerts

I want to create two separate data alerts that will be used to trigger automated emails to employees depending on the number of days they have to meet their project deadline. The data alerts must meet the following criteria:

• Alert 1: Data alert to email Certified employees with exactly 30 days until project deadline. I realize data alerts must be above or below a numerical threshold, so how can I measure this?
• Alert 2: Data alert to email Certified employees with an Overdue project status (i.e., negative days until deadline). Once the data alert meets the criteria of having a negative number of days, is there a way to prevent the alert from triggering the overdue items twice? The dataset will be refreshed every day, and I don't want the alert for overdue items to be triggered every single day, only once.