The best way to generate bar codes in Excel from data stored in cells
is to use a bar code ActiveX control. The best one on the market is
from TAL Technologies. Visit
www.taltech.com for more information.
You can also use bar code fonts however Code 128 is a complex
symbology that incorporates a special check digit so you cannot simply
select the cell containing the data that you want encoded in the bar
code and change its font to a Code 128 font and get a readable bar
code. Again the best way to do things is to use a Bar Code ActiveX
control.