Hi Taylor,
Following up on Ludek's comment, what barcode font are you using? I can't remember if XI still shipped the sample fonts. Those fonts were limited to uppercase and lowercase letters and numbers. No extra characters.
See if you can try with an extended Code39 font. If you use a regular font with the StringToCode39 formula, do you see "_" replacing the space? If you do then I would recommend a different barcode font. The function should be replacing spaces with "_".
If don't see the "_" then have a look at Azalea's website. They have a download for Crystal that have functions you can use in Crystal to convert to different barcode formats. Then you can try with their barcode as well.
Good luck,
Brian