如何计算指定线加总长度？

Sub GetSelectCurveLength()
       Dim SS As AcadSelectionSet
       Set SS = CreateSelectionSet
       Dim varType As Variant
       Dim varData As Variant
       BuildFilter varType, varData, 0, _
                             "ARC,CIRCLE,ELLIPSE,LINE,LWPOLYLINE,POLYLINE,SPLINE"
       SS.SelectOnScreen varType, varData
       Dim objEntity As AcadEntity
       Dim dblLength As Double
       For Each objEntity In SS
               dblLength = dblLength + GetCurveLength(objEntity)
       Next
       MsgBox "所选曲线的总长度为 " & dblLength, , "乐筑天下VBA示例"
End Sub
Public Function GetCurveLength(curve As AcadEntity) As Double
       Dim obj As VLAX, retVal
       
       Set obj = New VLAX
       
       obj.EvalLispExpression "(setq curve (handent " & Chr(34) & curve.Handle & Chr(34) & "))"
       obj.EvalLispExpression "(setq curvelength (vlax-curve-getDistAtParam curve " & _
                                                     "(vlax-curve-getEndParam curve)))"
       retVal = obj.GetLispSymbol("curvelength")
       obj.NullifySymbol "curve", "curvelength"
       
       '释放内存，函数返回
       Set obj = Nothing
       GetCurveLength = CDbl(retVal)
End Function
Public Sub BuildFilter(typeArray, dataArray, ParamArray gCodes())
       Dim fType() As Integer, fData()
       Dim index As Long, i As Long
       
       index = LBound(gCodes) - 1
               
       For i = LBound(gCodes) To UBound(gCodes) Step 2
               index = index + 1
               ReDim Preserve fType(0 To index)
               ReDim Preserve fData(0 To index)
               fType(index) = CInt(gCodes(i))
               fData(index) = gCodes(i + 1)
       Next
       typeArray = fType: dataArray = fData
End Sub
Function CreateSelectionSet(Optional SSetName As String = "mjtd") As AcadSelectionSet
       On Error Resume Next
       ThisDrawing.SelectionSets(SSetName).Delete
       Set CreateSelectionSet = ThisDrawing.SelectionSets.Add(SSetName)
End Function