Having limitted VBA programming experience (although enough to get
around), I would appreciate some advice on a design problem I'm facing.

I'm creating a table that allows the user to define expense line items
in terms of their characteristics and also apply various labels to each
line item in order to simplify and facilitate analysis. For example,
here's an example of some of the fields from one line item:

Opex Item: Marketing Acquisition: Customer Type A
Expense Type: Variable
Frequency: Month
Driver: Customer Type A - Gross Adds
Unit Cost: $100.0
Price ˆ†: -1.0%
Price ˆ† Period: Year
Threshold: $50.0 (min or max value)
Opex Category: Marketing
Provider: External
Provider Detail: Marketing Firm Name

My goal is to setup a function that takes these inputs and creates
output in a P&L or DCF output worksheet across a number of periods as
defined by the user. Does anyone have any guidance as to what form is
best for the output, i.e. values or equations/Excel functions? There
does need to be some level of description on how the formulas are
calculated or users will not trust the results.

For example, in the first case, I would have VBA code do all the
calculations and then just write the resulting values to the output
cells, i.e. $50,000 for mnth 24 expense. This is somewhat of a
blackbox for the user. I guess I could create a field in the output
area that showed the formula used.

In the second case, I would have VBA code create formulas, as if I
wasn't using VBA and was using Excel's non-VBA functionality only. A
simplified output might look something like:
=(CustAGrossAdds_t*$100*((1-PriceChange)^t)*12. Compared to the first,
this seems to use more processing power than necessary, but might be
more user friendly.

Am I looking at this incorrectly? Any help is appreciated.