Returns or sets the default envelope height, in points. Read/write Single.
Note If you set either the DefaultHeight or DefaultWidth property, the envelope size is automatically changed to Custom Size in the Envelope Options dialog box (Tools menu). Use the DefaultSize property to set the default size to a predefined size.
Example
This example sets the default envelope size to 4.5 inches by 7.5 inches.
With ActiveDocument.Envelope
.DefaultHeight = InchesToPoints(4.5)
.DefaultWidth = InchesToPoints(7.5)
End With