MarginRight Property

Returns or sets the distance (in points) between the right edge of the text frame and the right edge of the inscribed rectangle of the shape that contains the text. Read/write Single.

Example

Set myDocument = Worksheets(1)
With myDocument.Shapes.AddShape(msoShapeRectangle, _
        0, 0, 250, 140).TextFrame
    .AutoMargins = False
    .Characters.Text = "Here is some test text"
    .MarginBottom = 0
    .MarginLeft = 100
    .MarginRight = 0
    .MarginTop = 20
End With