实时错误3251  当前记录集不支持书签。？？这是为什么

Option Explicit
Dim mrc As ADODB.Recordset
Dim myBookmark As Variant
Dim mcclean As Boolean


Private Sub cancelCommand_Click()
 Unload Me
End Sub



Private Sub deleteCommand_Click()
  myBookmark = mrc.Bookmark
   
    If MsgBox("是否删除当前记录？", vbOKCancel, "删除当前记录") = vbOK Then
            mrc.MoveNext
            If mrc.EOF Then
                mrc.MoveFirst
                myBookmark = mrc.Bookmark
                mrc.MoveLast
                mrc.Delete
                mrc.Bookmark = myBookmark
                Call viewData
            Else
                myBookmark = mrc.Bookmark
               mrc.MovePrevious
                mrc.Delete
                mrc.Bookmark = myBookmark
                Call viewData
            End If
    Else
        mrc.Bookmark = myBookmark
        Call viewData
    End If
End Sub