Variable Name as dynamic field value for simulations

[#1]

I need to develop a simulation tool. The basic principle is the following:

Table_Values:

Item, Value

A, 10

B, 15

C, 20

Table_ImpactFactors:

Item, ImpactFactor

A, F1

B, F1

B, F2

C, F2

C, F3

F1, F2, F3 are variables to be independently set by the user for simulation (eg. with slider object)

The result should be a chart with

Dimension: Item

Expression: Value * sum(ImpactFactor) explanation => here the field value defines which variable to be used in the calculation

A = 10 * (F1)

B = 15 * (F1 + F2)

C = 20 * (F2 + F3)

By this user would be able to select the ImpactFactors to be considered, too (Selection activates the sliders)

Question: how to explain the chart, that the Field value is the name of the variable to be used ?