Nelson wrote:
Hello,

I have a worksheet with a column containing data in the format "###########"
I would like to change the values so that I can insert "dashes" at specific
locations, such as "##-####-####-#" for all the values in the column.

I tried the simple way...formating the cells, but when I run a formula, the
values don't match and I get an error, unless the dashes are actually
inserted.

Thank you in advance

what does the formula do?
After formatting is the cell text? May post your format code.