You can set a property to take a calculable value. For this, on the edit property page, check Calculable and put a script to the field Script. Use a script in OrientDB format.
Examples:
select sum(a, b) as value from MyClass where @rid = ?
select sum(e.salary) as value from Employee e where e.department = ? ```
In case of calculation just for a current row you can use short notation: ` sum(a, b)` instead of
```java
select sum(a, b) as value from MyClass where @rid = ?