I am working o a simple excel file. In one column, labeled "product id
code". This column has either 2 or 3 digit numbers in it. I need to
add an 8 or 9 digit number to every cell in front of the existing
number. Is there an easy way of doing this? Basically I am trying to
add a bar code prefix to each product id number. I am adding the same
number each time (either 89489800 or 894890 depending on if it is a 2
or 3 digit number. ) Right now I am just pasting it into every cell
and it is taking a while to do.

If Product ID Code is in Column B and contains the 2 or 3 digit
number, then select cell C2 and type this formula (assuming that the
first number is in cell B2):
=IF(LEN(B2)=2,"89489800"&B2,IF(LEN(B2)=3,"894890"&B2,""))
You can then copy and paste this formula as far down the C column as
you want (or you can drag down on the little black spot at the lower
right corner of cell C2).

Try this

If column A contains your data, enter this formula in column B
=A:A+8948980000

If you don't want to carry the formula, you can cut column B and
paste-special (values only) back to A then delete B.

Hope that helps,
- Alain