布尔运算的问题，请高手帮忙！

cottage

小弟做cad二次开发时遇到一个问题，请高手帮帮忙!

我是用vb调用cad做的，为了将来生成的程序能在不同版本之间运行，在开始没有引用cad库，采用了后绑定方式。用了很多命令很正常，但是在用布尔运算对实体进行编辑操作时发现了问题。用实体1减实体2，结果不论用求并集，交集还是1减2，结果都是交集。但是引用cad库后就能得出正常的结果了。怎么才能在后绑定状态（不引用cad库）下正常使用布尔运算？程序段如下:

Private Sub buer()
Dim sliceobj(1 To 1000) As Object
    Dim length As Double
    Dim width As Double
    Dim height As Double
    Dim center(0 To 2) As Double
    center(0) = 4.5: center(1) = 4.5: center(2) = 4.5
    length = 9: width = 9: height = 9#
   
    ' 在模型空间中创建长方体 (3DSolid) 对象
    Set sliceobj(1) = moSpace. _
                AddBox(center, length, width, height)
                ' 对立方体进行开挖
' Define the cylinder
    Dim cylinderObj As Object
    Dim aaa As Object
    Dim cylinderCenter(0 To 2) As Double
    Dim cylinderRadius As Double
    Dim cylinderHeight As Double
    cylinderCenter(0) = 4.5: cylinderCenter(1) = 4.5: cylinderCenter(2) = 0#
    cylinderRadius = 3#
    cylinderHeight = 20#
   
    ' Create the Cylinder (3DSolid) object in model space
   
    Set cylinderObj = moSpace.AddCylinder(cylinderCenter, cylinderRadius, cylinderHeight)

' 对立方体进行开挖

   sliceobj(1).Boolean acSubtraction, cylinderObj

'acadDoc.Regen True
acadDoc.Application.ZoomExtents
End Sub

请高手帮帮忙，十分感谢！