Cat,
Yes it is doable. You will need to import the module file first to your spreadsheet, and then calls Code128A or other functions.
You may take a look at our Excel sample.
To import th defintions of encoder functions, select Tools -> Macro -> Visual Basic Editor. When VB editor is open, select File -> Open. Navigate to the c:\program files\common files\morovia\moroviafonttools folder and select MoroviaFontTools.vbs. Close the VB editor and save the spreadsheet.
After you have the definitions of encoder functions, you can use them in your spreadsheet. For example, you can define cell C2 as
=Code128A(C$1)
Format C2 with our font you get the barcode in cell C2.
You can verify if the result is valid by comparing it with the one from FontPal.
More information can be found here:
http://www.morovia.com/font/support/font-tool.asp