I cannot use em or en dashes in a program that I use for work. I had a bit of trouble finding how to override the defaults in MS Word 2010 that I could not just change by clicking on Autocorrect. I had to change the defaults so that I could create my document in Word 2010 and then copy it to the program I use for work. This site told me how to override the em/en defaults:

http://office.microsoft.com/en-us/word-help/automatically-format-hyphens-as-en-dashes-and-em-dashes-HA010210087.aspx?CTT=1

The info is on the second half of the page.