Simulate the result of a Attribute calculation

I want to show the current value for a attribute and the final value for the value in the next level. Let’s say I have an effect add 2 to a value and the current base value is 10 and the base value for the next level is 20. So I want to show 12 > 22.
I found FAggregator::EvaluateWithBase which calculates a float value but there is no way to get the aggregator.

Do you know if it is actually possible to do?