You might have seen some sample codes of OLE. The way they get the object, and then get/set attribute.
The VB macro code for setting background to 25% darker gray would be:
ActiveDocument.Background.Fill.ForeColor.ObjectThemeColor = wdThemeColorBackground1
ActiveDocument.Background.Fill.ForeColor.TintAndShade = -0.25
ActiveDocument.Background.Fill.Visible = msoTrue
ActiveDocument.Background.Fill.Solid
You have to execute these commands using OLE.