You can use google flights.
See the support pages.
You can search up to 5 destinations at a time
Restrict to Sky Team
Set firm outbound date
Change return date and use + or – 2 days, repeat with new return date.
Example: Outbound is day 1. Earliest return is day 6.
First search is return day 8, +- 2 days
Next is return day 13, then day 18, etc. until you’ve either planned to move there or found what you want.
More ITA coding info
here