Hi Geri,
We have changed the data validation logic with our source, we have prepared a sample based on your requirement and we have attached the sample and documentation for your reference.
[Sample link]: http://www.syncfusion.com/downloads/Support/DirectTrac/General/DataValidation_demo-56417553.zip
[Documentation link]: http://www.syncfusion.com/downloads/Support/DirectTrac/General/DataValidation_Doc-378891775.zip
Please let us know if you have any concerns.
Regards,
Karthikeyan.