Excel case (whose very long and full name is Excel Change Case to Proper, Upper, Lower & Sentence Software) is a plugin to add to MS Excel that will add a function to change from uppercase to lowercase, and vice versa, very similar to the function which brings the MS Word by default.
Having the practical Excel Case plugin you can get much more juice to the MS Excel, because it allows you to select the cells of the spreadsheet that you want to modify, and, once selected, you only have to indicate if the texts of each cell you want to convert completely uppercase or lowercase.
Excel Case only works for MS Excel 2000 or higher.
You can free download Excel Case 32, 64 bit and safe install the latest trial or new full version for Windows 10 from the official site.