A little deeper

We need to think about what the minimum viable change (MVC) for starting this application. I am tending toward the interaction between different planning variables in the same hierarchy.

Sales Planning

Typically, there are three main variables used for sales planing. Last Year Sales, Expected Sales This Year, and Percent Change (LY vs TY). Last Year Sales (LY_SALES) should be locked as they can not be changed by the planner (normally some sort of ETL will get this data). This year expected sales (TY_SALES) is defined as LY_SALES * (1 + SALES_PERCENT). Conversly, percent change (SALES_PERCENT) is defined as TY_SALES/LY_SALES -1. The person doing the planning need to be able to enter the number in either TY_SALES or SALES_PERCENT and have it update the other value.

Class design

Based on the above we need to have something like

class PlanVariable
{
    private decimal value;
    private bool locked;
    private string name;

    public PlanVariable(string name, decimal currentValue, bool locked)
    {
        this.value = currentValue;
        this.locked = locked;
        this.name = name;
    }

    public decimal Value => value;
    public bool Locked => locked;
    public string Name => this.name;
}

We will also need to add in some eventing for letting other variable know when we have had are value changed.