I'm trying to automate a surface trim using a fit spline. What I have here is not working - when the AddTrimmingLoop2 function is called, Solidworks crashes. No debugging error, just a hard crash. The spline values are found using the 'Get BCurve Spline Points' Example, and is a single, closed spline describing the trim I want to occur. Does this function require more that one curve? Or does the surface need to be created within the scope of the function in order to access the TrimmingLoops?

Is there a better way of going about this?

'Function takes the cut curves data and trims the main surface (in the form of persistent sketch splines)
'
Function TrimCurves(swModel As SldWorks.ModelDoc2, swSelMgr As SldWorks.SelectionMgr, CutArr() As Variant, persistID() As Variant) As Boolean
Dim swFeat                   As SldWorks.feature
Dim swSketch               As SldWorks.Sketch
Dim bret                        As Boolean
Dim swSelData              As SldWorks.SelectData
Dim i                             As Integer
Dim j                             As Integer
Dim lastFeat                  As SldWorks.feature
Dim typeName               As String
Dim vFaceArr                 As Variant
Dim uFace                     As SldWorks.Face2
Dim cutSurface              As SldWorks.Surface
Dim mainSurf                 As SldWorks.Surface
Dim vBody                     As Variant
Dim swBody                  As SldWorks.Body2
Dim sBodySelStr            As String
Dim sPadStr                  As String
Dim sBodyTypeSelStr     As String
Dim vSketchSeg             As Variant
Dim swSketchSeg          As SldWorks.SketchSegment
Dim noSpline                 As Boolean
Dim segString                As String
Dim isGood                    As Boolean
'Spline parameters
Dim numCurves           As Long
Dim Order                   As Long
Dim Dimen                  As Long
Dim Periodic                As Long
Dim NumKnots            As Long
Dim NumCtrlPoints       As Long
Dim Knots()                 As Double
Dim CtrlPointsDbl()       As Double
Dim UVRange(3)          As Double
    'Force Rebuild
    bret = swModel.ForceRebuild3(True)
    
    'Set data
    Set swSelData = swSelMgr.CreateSelectData
    
    'Find surface body
    vBody = swModel.GetBodies2(swSheetBody, True)
    For j = 0 To UBound(vBody)
        Set swBody = vBody(j)
        sBodySelStr = swBody.GetSelectionId
        Debug.Print "  " & sPadStr & sBodySelStr
        
        Select Case swBody.GetType
            Case swSolidBody
                sBodyTypeSelStr = "SOLIDBODY"
                
            Case swSheetBody
                sBodyTypeSelStr = "SURFACEBODY"
                'get body faces
                vFaceArr = swBody.GetFaces
                Set mainSurf = vFaceArr(0).GetSurface
                'Select surface body
                'bret = swModel.Extension.SelectByID2(sBodySelStr, sBodyTypeSelStr, 0#, 0#, 0#, True, 0, Nothing, swSelectOptionDefault): Debug.Assert bret
                
            Case Else
                Debug.Assert False
        End Select
    Next j
    
For i = 0 To UBound(persistID)
    'Set swSelData = swSelMgr.CreateSelectData
    Set swSketchSeg = swModel.Extension.GetObjectByPersistReference3(persistID(i), Empty)
    bret = swSketchSeg.Select4(False, swSelData)
    segString = swSketchSeg.GetType
    
'Ensure spline inputed as a sketch segment
    If swSketchSeg.GetType = 3 Then
        'Find the spline parameters to pass to the trimming loop
        bret = SplineParams1.splineParameters(swSketchSeg, Order, Dimen, Periodic, NumKnots, NumCtrlPoints, Knots, CtrlPointsDbl, UVRange)
    Else
        noSpline = True
    End If
    
    numCurves = 1
    UVRange(0) = 0
    UVRange(1) = 1
    UVRange(2) = 0
    UVRange(3) = 1
    
    'Create the trimming loop on the Surface
     isGood = mainSurf.AddTrimmingLoop2(numCurves, Order, Dimen, Periodic, NumKnots, NumCtrlPoints, Knots, CtrlPointsDbl, UVRange)
Next i
End Function