I plan on updating an old VBA model by creating a .dll in visual studio and calling functions in VBA. This way, the users interact with the same looking excel file... but the functions are much faster and more powerful. I have everything working, what are the downsides to this? Are there any issues you've encountered that I'm not thinking of unrelated to the install process? I'm brand new to a concept like this, I usually create crappy windows forms for myself, what could go wrong?