Excel modules? OK not quite exactly the same but close.
I wrote a finite capacity planner system for a factory a fair few years ago in Excel to replace a huge number of Lotus 1-2-3 thingies with a vast amount of copy n paste from text screens and random sheets and what not.
I started with an automated forecast. We used an (memory may be fading) exponential fit which worked best using previous four weeks. eg last four Mondays would generate next Monday's demand.
The forecast could be tweaked by Planning at any time (aaaaiiiieee - Christmas!) The forecast was then fed into prep, make, bake, wrap and then dispatch. Between each process there is a stock holding. This is food so there are quite a few constraints on time, that's why we are making to forecast and not order. The customer will generally order your forecast if you are good enough and that is the whole point in the supply chain to the multiples: you know better than they do what will sell of your product.
The forecast cranks through the processes and stock points and generates a basic plan. It shows what efficiency is needed from each machine and the amount of manning etc. Oh dear you've got a Rademacher running at 170% which is a bit unlikely (110% is fine because 100% does not mean what you think it does in this industry - its a rate that is easy to achieve and not the absolute max). Oh and that machine is due 10 hours maintenance. Crap. OK, Mel off of Planning: do your thing ... a few parameters are tweaked, some production is offloaded to another member of the group and a packet of Hobnob biscuits is dispatched to a factory 200 miles away. The amended plan is run back through the model to ensure it satisfies the inputs and then when that is OK it is fixed for now.
I have not given too many details here as to specifics. I used a huge number of vlookups and I had a lot of code that ran through tables looking for the word "End" to indicate the last row (but one).
I basically found that VB gave me enough logic and whatever to get the job done in a reasonably safe way but without getting in the way of the business logic. I could concentrate on getting the job done.
Nowadays I'm a Linux (Windows and NetWare (lol)) sysadmin who masquerades as a PHB or MD but I still have a fondness for VBA. I recall getting someone's neural network spreadsheet VBA monster working after the most unlikely helpdesk call ever.
Good times.