Barcodes are just another type of font. excel comes with
one barcode fond call 3 of 9 barcode. Just change the font
of the cell you want to display barcodes to font 3 of 9
barcode. all bar code readers i have delt with can read 3
of 9 barcode.
If you go Format>Cells>Font, and you don't see a BarCode font, then you need
to install one, i.e. find it on the 'Net, possibly pay for it, download and
intall it.