The Idea is to concatenate the MakeID and YearID for matching using the MySQL CONCAT Function.
the recordset for the make dropdown list will need to be a joined query to pull the makes for the selected year:
SELECT Make.MakeID, Make.MakeName, BaseVehicle.YearID, CONCAT(BaseVehicle.MakeID, BaseVehicle.YearID) AS yearMake
FROM Make
INNER JOIN BaseVehicle
ON Make.MakeID = BaseVehicle.MakeID
in the Create Dynamic Array behavior:
Parent ID = YearID
Child ID = yearMake
Child Text = MakeName
And the recordset for the BaseVehicle Dropdown list will be:
SELECT *, CONCAT(MakeID, YearID) AS yearMake FROM BaseVehicle
and in the create Dynamic array:
Parent ID = yearMake
Child ID = BaseVehicleID
child Text = BaseVehicalName
