個別値分類のシンボルを特定したフィーチャから判断して更新する方法

Public Sub subChangeSymbolFromFeature()
    'ThisDocumentの取得
    Dim pMxDocument As IMxDocument
    Set pMxDocument = ThisDocument
     
    'アクティブなデータフレームの取得
    Dim pMap As IMap
    Set pMap = pMxDocument.FocusMap
     
    '最上位レイヤの取得
    Dim pLayer As ILayer
    Set pLayer = pMap.Layer(0)
 
    '特定フィーチャの取得
    Dim pFeatureLayer As IFeatureLayer
    Set pFeatureLayer = pLayer  'QI
     
    Dim pFeatureClass As IFeatureClass
    Set pFeatureClass = pFeatureLayer.FeatureClass
     
    Dim pFeature As IFeature
    Set pFeature = pFeatureClass.GetFeature(0)
     
     
    'レンダラの変更
    Dim pGeoFeatureLayer As IGeoFeatureLayer
    Set pGeoFeatureLayer = pLayer   'QI
     
    Dim pUniqueValueRenderer As IUniqueValueRenderer
    Set pUniqueValueRenderer = pGeoFeatureLayer.Renderer
     
    'レンダラで使用しているフィールド名の取得（複数フィールドを使用している場合）
    Dim sField1 As String
    Dim sField2 As String
    Dim sDeliniter As String
    Dim sValue As String
     
    sField1 = "num"
    sField2 = "Test"
    sDeliniter = pUniqueValueRenderer.FieldDelimiter
     
    sValue = pFeature.Value(pFeatureClass.FindField(sField1)) & sDeliniter & _
                pFeature.Value(pFeatureClass.FindField(sField2))
     
    '対象フィーチャの使用しているシンボルを取得
    Dim pSimpleMarkerSymbol As ISimpleMarkerSymbol
    Set pSimpleMarkerSymbol = pUniqueValueRenderer.Symbol(sValue)
     
    '取得したシンボルの色を変更
    Dim pRGB As IRgbColor
    Set pRGB = New RgbColor
     
    pRGB.RGB = vbRed
    pSimpleMarkerSymbol.Color = pRGB
     
    'TOC、マップの再描画
    pMxDocument.UpdateContents
    pMxDocument.ActiveView.Refresh
     
End Sub