Hide a user field from the masks of SAP with SDK

Question

Hello everyone,
how I can hide a user field on a form?
I think there are two solutions:
1) I can use the event "Form_Load" and change the property "visible" for the user field (bad)
2) I think the best solution is to modify the configurations of the form, hiding the field for all users.
I tried this with the example I write below, but the addon correctly change the values ​​in the table "CPRF​​", but still shows the SAP field and then when I close the program, the values ​​are reset again.
I ask your help please. How I can do?
thanks
Info
SAP 8.81 PL09
SQL2008 DB
            Dim frmPref As FormPreferencesService
            Dim colPrefs As ColumnsPreferences
            Dim colPrefsPrm As ColumnsPreferencesParams
            Dim col As SAPbobsCOM.ColumnPreferences = Nothing
            '_SboCy  ==> SAPbobsCOM.Company
            '_sboCys ==> SAPbobsCOM.CompanyService
            'get Form Preferences Service
            frmPref = CType(_sboCys.GetBusinessService(ServiceTypes.FormPreferencesService), FormPreferencesService)
            'get Columns Preferences Params
            colPrefsPrm = CType(frmPref.GetDataInterface(FormPreferencesServiceDataInterfaces.fpsdiColumnsPreferencesParams), ColumnsPreferencesParams)
            'set the form id (e.g. A/R invoice=133)
            colPrefsPrm.FormID = "-139"
            'set the user id (e.g manager= 1)
            colPrefsPrm.User = 1
            'get the Columns Preferences according to the formId & user id
            colPrefs = frmPref.GetColumnsPreferences(colPrefsPrm)
            Dim exist As Boolean = False
            'change the width of all the visible items
            For i As Integer = 0 To colPrefs.Count - 1
                If colPrefs.Item(i).ItemNumber = "U_MYFIELD" Then
                    colPrefs.Item(i).VisibleInForm = BoYesNoEnum.tNO
                    colPrefs.Item(i).EditableInForm = BoYesNoEnum.tNO
                    exist = True
                    Exit For
                End If
            Next
            If Not exist Then
                col = colPrefs.Add
                col.Column = "-1"
                col.EditableInExpanded = BoYesNoEnum.tNO
                col.EditableInForm = BoYesNoEnum.tNO
                col.FormID = "-139"
                col.User = 1
                col.ExpandedIndex = 1
                col.Width = 0
                col.VisibleInExpanded = BoYesNoEnum.tNO
                col.VisibleInForm = BoYesNoEnum.tNO
                col.ItemNumber = "U_MYFIELD"
            End If
            'Update
            frmPref.UpdateColumnsPreferences(colPrefsPrm, colPrefs)
            NothingObj(CObj(col))
            NothingObj(CObj(frmPref))
            NothingObj(CObj(colPrefs))
            NothingObj(CObj(colPrefsPrm))

Answer 1

Hello Joris,
I searched on help.sap.com and found the following link, it provides the constraints LDAP and UME sync has.
http://help.sap.com/saphelp_nw70/helpdata/EN/48/d1d13f7fb44c21e10000000a1550b0/frameset.htm
Regards,
Siddhesh