You can use this relevance with the REST API:
And put the relevance from above behind it:
https://x.x.be:52311/api/query?relevance=names of bes fixlets whose ( month_and_year of source release date of it = (month_and_year of current date - 1*month) and display name of site of it contains "Patches for Windows" and source severity of it contains "Critical")
More info can be found on https://developer.bigfix.com/rest-api/ .
Hope this helps!