It sounds like you want to insert an Excel (xls format) object at the cursor of an e-mail message. To do that you need to take control of the WordEditor inspector related to the message and then the vba is pretty much the same as it would be for Word itself, and you can probably use the Word VBA editor to record a similar process to adopt. The main issue is that you cannot use Word specific commands e.g. those beginning 'wd'. For those you need to use the numeric equivalents and you must define Word variables as Objects, as in the case of Dim oRng.
Sub InsertAnObject()
Dim oRng As Object
Const strFilename As String = "C:\Users\File.xls" 'The Excel file to be inserted
On Error GoTo ErrHandler
If TypeName(ActiveWindow) = "Inspector" Then
'ensure that the cursor is in the body of the message
If ActiveInspector.IsWordMail And ActiveInspector.EditorType = olEditorWord Then
'Set a range to the cursor position
Set oRng = ActiveInspector.WordEditor.Application.Selection
'Insert the file at the range
oRng.InlineShapes.AddOLEObject _
ClassType:="Excel.Sheet.8", _
fileName:=strFilename, _
LinkToFile:=False, _
DisplayAsIcon:=False
End If
End If
lbl_Exit:
Exit Sub
ErrHandler:
Beep
Resume lbl_Exit
End Sub