This example sets the default custom envelope width and height and adds an envelope to the active document.
addr = "Tim O' Brien " & vbCr & "123 Skye St." _
& vbCr & "Bellevue, WA 98004"
ret = "Dave Edson" & vbCr & "123 West Main" _
& vbCr & "Seattle, WA 98004"
With ActiveDocument.Envelope
.DefaultWidth = InchesToPoints(9)
.DefaultHeight = InchesToPoints(3.85)
End With
ActiveDocument.Envelope.Insert Address:=addr, ReturnAddress:=ret