did you find a good solution to this?
The only solution i can think of is a series of 30 properties, every day ue a workflow to copy the total number of sessions to a (-1 day) property, the next day that would get copied to (-2 days) and so and so forth. After 30 days, you have the (-30 days) property with the number of sessions the contact had 30 days ago so you can then use a calculated property to find the number of sessions in the last 30 days. ((-30 days)-(total sessions)) which would give you what you’re looking for! this is not an elegant solution by any means though so i’m curious if you came up with anything better