What would be the simplest way, lets say i have an excel spreadsheet, would want to share it online for "specific" users to edit it, but restrict them from making copies/download of the file because i would want to keep the formula's to myself.

tried google sheets, but cant do it
tried dropbox, cant do it too

google sheets "editors" can download but can prevent "viewers" from downloading.

i want to be able to provide edit access to my members but not want them to download.

Thanks