Custom validation error can not be handled in spreadsheet
https://dojo.telerik.com/@zdravkov/uJuruCod
go to Data->Data Validation->Custom Formula (Ignore blank, Reject input),
open the console,
than if you enter an invalid formula (<4, >A3 or something like this) and press Apply, in the console you can see an exception
The exception can't be handled
One should be able to handle the exception
workaround - https://dojo.telerik.com/@zdravkov/adEWOlOk