请教一个moving feedback的问题

<P>我按照ao帮助上面的moving feedback的例子</P>
<P>Private m_pAV As IActiveView</P>
<P>Private m_pGraCont As IGraphicsContainer</P>
<P>Private Function GetHitElement(pInPt As IPoint) As IElement
  Dim pEnumElem As IEnumElement
  Dim DblSrchDis As Double</P>
<P>Set m_pGraCont = m_pAV
  
DblSrchDis = m_pAV.Extent.Width / 200
  
Set pEnumElem = m_pGraCont.LocateElements(pInPt, DblSrchDis)
  
  If Not pEnumElem Is Nothing Then
    Set GetHitElement = pEnumElem.Next
  End If</P>
<P>end function
别的就不粘贴了，小弟有两个问题想请高手帮忙</P>
<P>1。为什么pEnumElem 总是nothing</P>
<P>2。我选择不出pEnumElem，我只能选择一个Feature,IElement和IFeature之间能不能转化</P>

<P>m_pAV怎么实例化的？</P><P>

 </P>