Yes, use precedence constraints to handle the first part of your requirements. As far as the second part, whether or not your package has run this month, you'll have to come up with a way to track package executions. You could query the SSISDB internal operations table to find the last run. Another option is to track your package executions in your own tables. I typically create a set of table to track my package stats for run times, rows staged, errors, etc. This also gives you a way to query to determine if you've run this month already. Combine the result from this query with your override parameter and you can create a solve for this requirement.