In Salesforce, task driven workflow is important and we often have the need to trigger a workflow rule when a task is completed. For example, when the first initial contact call is made, update the status and create a follow-up task. Below is a workflow rule where we make use of the “Latest Activity Subject” field to do this. The “Latest Activity Subject” field always contains the subject of the last completed task. The rule below will be triggered when a task with the subject “Make initial contact call” is completed. Immediately upon completion of the task you you will see the Status update to Contacted and a follow-up task will be automatically be created and assigned to the owner with a due date in 7 days.
Trigger workflow rule when multiple tasks are completed
You may also find the need to trigger an event when a combination of tasks have been completed. To do this you would utilize the “Task Completed” field (API name: ezwf__Easy_Workflow__c). This is a rollup field which contains the subject of every completed task. Below is a rule which will triggered when all 3 tasks have been completed. Note that we use the “CONTAINS” operator for this type of rule.
If your requirement is more complicated you can create a formula field and reference it in your workflow rule. For example, you can create a formula field which equals True when a combination of 10 tasks are completed and any combination of fields have your specified value. Then just create a workflow rule which triggers when the formula field equals True.