要重定义块，请使用 Block 对象的任何方法和特性。重定义块时，图形中对该块的所有参照也随即更新，以便反映新的定义。
重定义会影响以前和以后的块插入。固定属性会丢失，并且被新的固定属性所替换。即使新块不包含属性，可变属性也保持不变。
本例创建一个块并向块定义中添加一个圆，然后将块作为块参照插入到图形中。块定义中的圆将被更新，块参照也会自动更新。
Sub Ch10_RedefiningABlock()
' 定义块
Dim blockObj As AcadBlock
Dim insertionPnt(0 To 2) As Double
insertionPnt(0) = 0
insertionPnt(1) = 0
insertionPnt(2) = 0
Set blockObj = ThisDrawing.Blocks.Add _
(insertionPnt, "CircleBlock")
' 向块中添加圆
Dim circleObj As AcadCircle
Dim center(0 To 2) As Double
Dim radius As Double
center(0) = 0
center(1) = 0
center(2) = 0
radius = 1
Set circleObj = blockObj.AddCircle(center, radius)
' 插入块
Dim blockRefObj As AcadBlockReference
insertionPnt(0) = 2
insertionPnt(1) = 2
insertionPnt(2) = 0
Set blockRefObj = ThisDrawing.ModelSpace.InsertBlock _
(insertionPnt, "CircleBlock", 1#, 1#, 1#, 0)
ZoomAll
' 重定义块中的圆，
' 并更新块参照
circleObj.radius = 3
blockRefObj.Update
End Sub