怎样获得点到曲线的垂足

Sub GetClosestPoint()
    'ThisDrawing.SendCommand "(vl-load-com)" & vbCrLf
    '定义引用曲线类模块
    Dim ObjCurve As Curve
    Set ObjCurve = New Curve
    '获取曲线
    Dim Pnt As Variant
    Dim Ent As AcadEntity
    ThisDrawing.Utility.GetEntity Ent, Pnt, "选择曲线："
    '亮显刚选定的曲线以方便捕捉曲线上的点
    Ent.Highlight True
    '捕捉曲线上的一个点
    Pnt = ThisDrawing.Utility.GetPoint(, "选择曲线外的一点：")
    '通过曲线类模块获取曲线距离选取点最近的点
    Set ObjCurve.Entity = Ent
    Dim ClosestPnt As Variant
    ClosestPnt = ObjCurve.GetClosestPointTo(Pnt)
    '显示曲线长度
    MsgBox "曲线上距离选取点最近的点坐标为：" & vbCrLf & vbCrLf & ClosestPnt(0) & "," & ClosestPnt(1) & "," & ClosestPnt(2), , "乐筑天下VBA示例"
    '取消曲线的亮显
    Ent.Highlight False
    '释放变量
    Set ObjCurve = Nothing
End Sub