How to define a custom delegate for an event in IDL

Events.idl

runtimeclass Events;

[version(1.0), uuid(da38922c-3d3a-404f-8477-de9c104c4f34)]
delegate HRESULT CustomDelegate([in] int value);

[version(1.0), uuid(6ac35d2c-b2cf-4c36-995c-a9c0764636c9), exclusiveto(Events)]
interface IEvents : IInspectable
{
    [eventadd] HRESULT CustomEvent([in] CustomDelegate* handler, [out][retval] EventRegistrationToken* cookie);
    [eventremove] HRESULT CustomEvent([in] EventRegistrationToken cookie);
};

[version(1.0), activatable(1.0), static(IEventsStatics, 1.0)]
runtimeclass Events
{
    [default] interface IEvents;
};