PresetExtrusionDirection Property Example
This example changes each extrusion on myDocument that extends toward the upper-left corner of the extrusion's front face to an extrusion that extends toward the lower-right corner of the front face.
Set myDocument = ActiveDocument
For Each s In myDocument.Shapes
    With s.ThreeD
        If .PresetExtrusionDirection = msoExtrusionTopLeft Then
            .SetExtrusionDirection msoExtrusionBottomRight
        End If
    End With
Next