You can use bar code fonts in Excel however they generally produce
very poor quality bar codes and they also require you to add
start/stop characters and also calculate a check digit for each
message that you want to encode.
If you want to produce exceptional quality, device independent, bar
codes where you do not need to calculate or add anything to the data
being encoded, then the best approach would be to use a bar code
ActiveX control that is not based on a font.
The best one on the market is from TAL Technologies. You can download
a demo version of it from the following web page:
http://www.taltech.com/products/activex_barcodes.html
The demo version of the TAL Bar Code ActiveX control comes with a
sample Excel spreadsheet that demonstrates how to use it in Excel.