Hello Diana,
I would recommend reviewing this Regular Expression site anytime you need to browse for an existing regular expressing that you can re-use:
http://regexlib.com/ Also, once you find a regular expression you want to use, it's always a good idea to test the Regular Expression that you gathered at a location such as here:
http://www.softlion.com/webTools/Re...fault.aspx After confirming the validity of your Regular Expression then I would recommend using it within a Dynamic Form Question validation.
Please let me know if you have any questions.
Thanks,
Ryan