Hi Paul,
Thank you for using Syncfusion products.
We have prepared the simple sample to meet your requirement.
In this sample, we have used the Command binding for Items inside the "Clipboard" RibbonBar in Home RibbonTab. While executing the Command, shown the header of Button in MessageBox.
You can download the sample from the below location:
Sample:RibbonSample_in_MVVM
Regards,
Priyanga B