expression.MarginBottom
expression Required. An expression that returns a TextFrame object.
Example
This example adds a rectangle to myDocument, adds text to the rectangle, and then sets the margins for the text frame.
Set myDocument = ActiveDocument
With myDocument.Shapes.AddShape(msoShapeRectangle, _
0, 0, 250, 140).TextFrame
.TextRange.Text = "Here is some test text"
.MarginBottom = 0
.MarginLeft = 100
.MarginRight = 0
.MarginTop = 20
End With