Redwood VBS: How to default the salary amount when hiring an employee

Summary:

Hello,
Customer requires a way of defaulting the value of "Salary Amount" when performing a hiring.
As per current design, Grade structures consists of some Grade Rates with min and max and some others with a specific value. These are reflected as Valid Grades in Positions and also in a Salary Basis.

Our goal is, by means of a VBS Business Rule, to default the proposed "Salary Amount" before submitting the hire. I'd like to know whether is feasible to read and default the min, the max or the specific value of the proposed Position's Valid Grade.

I should say that, due to a cross implementation between Core HR and Compensation, using Progression Grade Ladders to achieve this is out of question.