Event handler for COM event of type OleVariant?

I have imported a type library.  The COM interface has some write only
event properties which are defined like this :
property OnDoSomeEvent : OleVariant write ....
I want to have an event handler for this event but can't seem to do
it.  I've tried the following sort of approach but don't know how to
typecast a method pointer to an OLEVariant.

procedure TForm1.OnCreate(Sender : TObject);
  OleCheck(CoCreateInstance(......., MyInstance));
  MyInstance.OnDoSomeEvent := SomeEventHandler;

How can I do this?