Hi Scott,
Thank you for contacting Telerik support.
Please, refer to this
KB Article, which describes how you can implement RadMultiSelectDropDownList.
I have prepared a small sample based on the article, which demonstrates how to create scenario similar to yours - please, refer to the attached sample project.
Could you share more details about the issue with our example, because I was not able to identify it.
Kind regards,
Peter
the Telerik team