This example sets the horizontal and vertical offsets of the shadow for shape three on myDocument
. The shadow is offset 5 points to the right of the shape and 3 points above it. If the shape doesn't already have a shadow, this example adds one to it. The shadow will be filled in and obscured by the shape, even if the shape has no fill.
Set myDocument = ActivePresentation.Slides(1)
With myDocument.Shapes(3).Shadow
.Visible = True
.OffsetX = 5
.OffsetY = -3
.Obscured = True
End With