Formula field for the Leads module that sums all related open and closed calls associated with the record

Formula field for the Leads module that sums all related open and closed calls associated with the record

Hello,

I wish to make a formula field inside the Leads module that counts/sums all the Open Calls and Closed Calls that are associated with the record. I plan to use this field to setup an automation where if a lead has a count of zero open and closed calls after 7 days have passed from the last modified time, send an alert to a manager. If there are any other suggestions, feel free to suggest it. Thanks so much in advance!