Hi Richard Harrigan,
I am afraid that RadDataFilter was not designed to support your specific requirements. It's visual structure was not meant for such kinds of filtering. It performs only simpler filters.
Your best option would be to build a custom user control from scratch which can have any UI. It can produce IFilterDescriptors in case you need to filter RadGridView. If that is not the case and you want to filter your data source directly, then your custom filtering user control does not need anything "Telerik's" inside it.
I hope this helps. Let me know if you have questions.
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