[求助]：vba中，如何实现物体捕捉？？？

wanghymj

在下面这个例子中，如何实现画线的顶点捕捉在物体？？？thanks very much!!!!!
Sub PlaceLine()
    CommandState.StartPrimitive New clsPlaceLineCommand
End Sub

Implements IPrimitiveCommandEvents

Private m_atPoints(0 To 1) As Point3dPrivate m_nPoints As Integer
Private Sub IPrimitiveCommandEvents_Cleanup()

End Sub

Private Sub IPrimitiveCommandEvents_DataPoint(Point As Point3d, ByVal View
As View)

    If m_nPoints = 0 Then
        CommandState.StartDynamics
        m_atPoints(0) = Point
        m_nPoints = 1
        ShowPrompt "Place end point"
    ElseIf m_nPoints = 1 Then
        m_atPoints(1) = Point
        Dim oEl As LineElement
        Set oEl = CreateLineElement1(Nothing, m_atPoints)
        ActiveModelReference.AddElement oEl
        oEl.Redraw
        m_atPoints(0) = m_atPoints(1)
    End If

End Sub


Private Sub IPrimitiveCommandEvents_Dynamics(Point As Point3d, ByVal View As
View, ByVal DrawMode As MsdDrawingMode)
    If m_nPoints = 1 Then
        m_atPoints(1) = Point
        Dim oEl As LineElement
        Set oEl = CreateLineElement1(Nothing, m_atPoints)
        oEl.Redraw DrawMode
    End If
End Sub

Private Sub IPrimitiveCommandEvents_Keyin(ByVal Keyin As String)

End Sub

Private Sub IPrimitiveCommandEvents_Reset()
    CommandState.StartPrimitive Me
    m_nPoints = 0
End Sub

Private Sub IPrimitiveCommandEvents_Start()
    ShowCommand "VBA PlaceLine Example"
    ShowPrompt "Select start of line"
End Sub

wanghymj

各位大虾：
帮帮我，急急！！！！！！！！！