Changes the vertical offset of the shadow by the specified number of points. Use the OffsetY property to set the absolute vertical shadow offset.
expression.IncrementOffsetY(Increment)
expression Required. An expression that returns a ShadowFormat object.
Increment Required Single. Specifies how far the shadow offset is to be moved vertically, in points. A positive value moves the shadow down; a negative value moves it up.
Example
This example moves the shadow for shape three on myDocument up by 3 points.
Set myDocument = ActivePresentation.Slides(1)
myDocument.Shapes(3).Shadow.IncrementOffsetY -3