Try this (adjust the adjustment number to suit (a number up to 1)
Sub rad_est()
Dim oshp As Shape
Dim osld As Slide
Set osld = ActivePresentation.Slides(1)
Set oshp = osld.Shapes.AddShape(Type:=msoShapeChevron, _
Top:=144, Left:=144, Width:=72, Height:=72)
oshp.Adjustments(1) = 0.3
End Sub
And I know the "myDocument" comes straight from Microsoft but a Slide is NOT a Document!