Help - Listing students who abandoned

[Aristotelis_T]

Hi, we are using appsheet to keep track of student history and I need to create a view/report with the students that have abandoned the classes (have no payment for 2 months).
I tried starting from a virtual column to build it inside-out but, I am simply… lost, sorry! Not even sure which approach to use (new view based on new slice, new table, virtual columns report… ??)

The scheme is simple: we have a Students table and a Payments table.
The key of the Payments table is a concatenation of the columns
» Course (name of course, unique string),
» Month (which holds the day 1 of the month of the respective payment)
» ContactID (ref to the ContactID column which is the key of the Contacts table)

How do I go about building this?
Any suggestions would be greatly appreciated