Inside Property
True if an inside border can be applied to the specified object. Read-only Boolean.
expression.Inside
expression Required. An expression that returns a Border object.
Example
If the current selection supports inside borders (that is, if multiple paragraphs or cells are selected), this example applies a single inside border.
Dim borderLoop As Border
For Each borderLoop In Selection.Borders
If borderLoop.Inside = True Then _
borderLoop.LineStyle = wdLineStyleSingle
Next borderLoop