Da fehlen Parameter. Versuche es mal so:
Set notesEmbeddedObject = notesRichTextItem.EMBEDOBJECT(1453, "", "D:\Header.png", "Header.png")
Aus der Notes Hilfe
Set notesEmbeddedObject = notesRichTextItem.EmbedObject( type%, class$, source$, [ name$ ] )
Parameters
type%
Constant. Indicates if you want to create an attachment, an embedded object, or an object link. May be any of the following:
EMBED_ATTACHMENT (1454)
EMBED_OBJECT (1453)
EMBED_OBJECTLINK (1452)
class$
String.
If you are using EMBED_OBJECT and want to create an empty embedded object from an application, use this parameter to specify the name of the application (for example, "1-2-3 Worksheet") and specify an empty string ("") for source$. Case-sensitive.
If you are using EMBED_OBJECTLINK or EMBED_ATTACHMENT, specify an empty string ("").
source$
String.
If you are using EMBED_OBJECT and want to create an embedded object from a file, use this parameter to specify the name of the file, and specify an empty string ("") for class$.
If you are using EMBED_ATTACHMENT or EMBED_OBJECTLINK, use this parameter to specify the name of the file to attach or link.
name$
String. Optional. Name by which you can reference the NotesEmbeddedObject later. This parameter is only used for OLE/2 objects and does not include attachments.
Andreas