From Xojo Documentation
Used to overload the Not operator, providing custom functionality.
Create an Operator_Not function in a class to specify the functionality of the Not operator for that class. Whenever you use the Not operator in your code to operate on two instances of the class, your Operator_Not function will be called.
In the function, the Self instance is the only operand. No parameters are passed.
Suppose you define a class MyResult with the property a as Boolean. Operator_Not is defined on the class as: