Hi Diepic,
Now let me describe my understanding of your scenario to see if it is correct:
1) ‘Racavi effettivi’ field is in the opportunity table? is it what you call total revenue?
2) 'Importo fatturazioni' field is on personal table? Does it refer to the ''payment'' you mentioned earlier?
3) personal table and opportunity table have N:1 relationship, one opportunity have many personal table records?
4) You need the total value of multiple "Importo fatturazioni" field values associated with the current opportunity, and then compare it with the ‘Racavi effettivi’ field value?
--Using the screenshot you provided as an example, you need (2.500,00 + 2.500,00) to compare with 10.000,000?
All of the above is correct?
If right, you can refer to the following:
You mentioned that you want to implement it in a low-code way, so you can create a new field on the opportunity table.
1)Make the field type is Rollup, and aggregate all payments for a record from related personal table records:
2)Using business rule to compare the new created field with total revenue(‘Racavi effettivi’ field).