Using vtkArrayCalculator to multiply a vector array by a single scalar value

It is clear how to use vtkArrayCalculator to multiply a vector array (point based) times a single scalar value. For example OutputVector = InputVector * 2.3.

But is it possible to define other variables instead of explicitly writing 2.3. For example:

a = 1.2
b = sqrt(a)
OutputVector = InputVector*b

.