TypeLib - 'Dispid out of range'

Hi,
I am trying to implement a sink object for HTMLElementEvents (D5 - IE4).
The type library editor display an error message, 'Dispid out of range',
when I am trying to set the dispid to --2147418101 (ondragstart).
I did some tests, and the behavior is a mystery to me:

1) Any dispid beginning with '-2' or '-3' cause the above error.
2) dispids beginning with '-1' or '-4', must have exactly 1 digit, otherwise
they cause the above error.
3) dispids beginning with '-5' to '-8', can either have 1 digit or three
digits, otherwise they cause the above error.
4) dispids beginning with '-9' must have exactly 3 digits, otherwise they
cause the above error.

A clue anyone ???

Thanks,

Oren Hollander.