思路如下：
1、建立选择集
2、用过滤器选择所有多线段


3、遍历选择集中所有对象，如果属性是闭合，则调用偏移方法，偏移距离-0.1就可以了



Dim sstext As AcadSelectionSet
Dim FilterType(0) As Integer
Dim FilterData(0) As Variant
Set ss = ThisDrawing.SelectionSets.Add("SS2")
FilterType(0) = 100
FilterData(0) = "AcDbPolyline"
ss.Select acSelectionSetAll ，，， FilterType, FilterData
dim obj as AcadLWPolyline
for each obj in ss
if obj.closed then obj.offset -0.1
next obj