There are several ways bar codes might be generated:
1. Have the application generate them graphically. This is the easiest approach because you don't have to do anything special as the functionality is built directly into your software. This is what VB does. The limitation is that VB cannot draw the image less than 1 pixel in size, and the next size up is 2 pixels and so on. This may not scale smoothly to exactly the sized font that you want.
2. Acquire and install an EAN-13 bar code font on your computer. Font scale technology in Windows does not have the same limitation of drawing (simple) graphics. You typically have a lot more control over the font's size using this approach.
3. Acquire a printer that has font printing capabilities and follow the instructions on how to print bar codes using it, in conjunction with Windows software.
Note: just because you can print a font of a certain size or scale, doesn't mean your bar code scanner can read it back. If a font is outside its normal size range, your scanner will not probably be able to recognise it.