You can try, but you realistically will never be able to convert all the finance/analyst type folks off Excel. Their workflows are too ingrained in how Excel does things (vbscript, proprietary extensions, even simple vlookup tables that need to be converted to work with Calc). Hackers will (rightly) complain that a lot of that is abuse of Excel and should be done in a proper programming language--you can either try to change the rest of the world or you buy some Office licenses and continue building your business.