Is it possible to change the thickness of a sheet metal part via API?

I have found in the api help the code to change the bend radius (see: 2014 SolidWorks API Help - Change Bend Radius of Sheet Metal Part Example (VBA) )

and added a few lines to change the thickness. But the thickness does not change.

What do I do wrong?

Here is the code i found and changed a little:

'-----------------------------------------------

'

' Preconditions:

'       (1) Part document containing sheet metal part is open.

'       (2) Sheet-Metal feature is selected.

'

' Postconditions: Default bend radius value is doubled.

'

'-----------------------------------------------

Option Explicit

Sub main()

    Dim swApp                   As SldWorks.SldWorks

    Dim swModel                 As SldWorks.ModelDoc2

    Dim swSelMgr                As SldWorks.SelectionMgr

    Dim swFeat                  As SldWorks.Feature

    Dim swSheetMetal            As SldWorks.SheetMetalFeatureData

    Dim bRet                    As Boolean

    Set swApp = Application.SldWorks

    Set swModel = swApp.ActiveDoc

    Set swSelMgr = swModel.SelectionManager

    Set swFeat = swSelMgr.GetSelectedObject5(1)

    Set swSheetMetal = swFeat.GetDefinition

MsgBox swSheetMetal.Thickness

    Debug.Print "Feature = " & swFeat.Name

    Debug.Print "  BendRadius = " & swSheetMetal.BendRadius * 1000# & " mm"

   ' Rollback to change default bend radius

    bRet = swSheetMetal.AccessSelections(swModel, Nothing): Debug.Assert bRet

    swSheetMetal.BendRadius = 2# * swSheetMetal.BendRadius

    swSheetMetal.Thickness = 2

MsgBox swSheetMetal.Thickness

   ' Apply changes

    bRet = swFeat.ModifyDefinition(swSheetMetal, swModel, Nothing): Debug.Assert bRet

MsgBox swSheetMetal.Thickness

End Sub

'-----------------------------------------------

Thanks in advance,

Henk Kemper