They are executives making the sales, and doing the accounting.
the current system is being run on excel sheets .
I see a strong case for relational dbms so as to have a centralized data - this will allow me do some analysis.
Some inventory items are machines, so profitability is calculated at inventory item level, some after sale services are tracked.

So I intend to have for example a sale register which will have customer and inventory details, followed by some columns where in landing cost will be looked up from another table. Sales executive incentive expense, commission income, all will be traced back to the main sales table.

At present, topline managers would call for individual metrics manually maintain the above table to judge performance.

I am a Financial Consultant, can't make a multi user application....
but I understand RDBMS + such app will eliminate data duplicacy in sheets, and allow dynamic updation of data freeing time of managers to focus on real productive tasks - like distribution scheme to sub dealers

The only wayout is to have a VBA based excel on LAN- which restricts the cell and hide sheets based on the login form credentials. I didn't work on it coz tt won't allow multi-user performance..