At my current workplace we have a few workbooks that need to be updated any time that our customer provides us with an update to them. Unfortunately they never tell us what changed so we have to go through and redo all the changes that we did previously and apply them to the new workbook. Then we have to test if we didn't mess something up in the migration and whatnot; all in all it takes upwards of a month between managerial overhead and the time it takes to actually figure out where something got messed up. And there's no good diff tool for excel documents which makes it incredibly frustrating to try and find what one cell might be wrong between a working document and an incorrect document. And then VBA for macros is basically impossible to understand because any googling for it returns results for every other version of VB with slight differences that don't work in Excel.