The VarType property provides read-only access to the type code that identifies a custom Variant data type. 

The value of VarType is set in the constructor. This can be an automatically generated value, or it can be a value explicitly passed to the constructor. Note that if the VarType is automatically-generated, it may not remain the same for every application that uses the custom Variant type: its value will depend on the other custom Variants also used in the application. 

TVarData 

Create 

VarType 

FindCustomVariantType 

Enabling Casting