I once worked for a company where the accountants had written a massive and convoluted VBA application that had gradually become mission critical to the company

I once worked for a company where the accountants had written a massive and convoluted VBA application that had gradually become mission critical to the company. The IT department allocated a number of people (half a dozen?) for some time (8-12 months?) trying to turn it into a maintainable software product. They failed.