expression.PercentWidth
expression Required. An expression that returns a HorizontalLineFormat object.
Remarks
Setting this property also sets the WidthType property to wdHorizontalLinePercentWidth.
Example
This example adds a horizontal line and sets its length to 50% of the window width.
Selection.InlineShapes.AddHorizontalLineStandard
ActiveDocument.InlineShapes(1) _
.HorizontalLineFormat.PercentWidth = 50