Sub MergeLayers()
  Dim pMxDoc As IMxDocument
  Dim pMap As IMap
  Dim pFeatureLayer As IFeatureLayer
  Dim pInFeatureClass As IFeatureClass
  Dim pOutFeatureClass As IFeatureClass
  
  Set pMxDoc = ThisDocument
  Set pMap = pMxDoc.FocusMap
  Set pFeatureLayer = pMxDoc.SelectedLayer
  Set pInFeatureClass = pFeatureLayer.FeatureClass
  '=======================================================================
  Dim ET As New ETGW_Core
  Dim sOutFileName As String
  Dim pLayerToMerge As IFeatureLayer
  Dim pFeatureClassToMerge As IFeatureClass
  'an exaple on how to get a feature layer by name
  Set pLayerToMerge = ET.GetLayer("layer2")
  If pLayerToMerge Is Nothing Then
    Exit Sub
  End If
  Set pFeatureClassToMerge = pLayerToMerge.FeatureClass
  sOutFileName = "c:\00\merged.shp"
  Set pOutFeatureClass = ET.Merge(pInFeatureClass, pFeatureClassToMerge, _
                                sOutFileName)
  '========================================================================
  Set pFeatureLayer = New FeatureLayer
  Set pFeatureLayer.FeatureClass = pOutFeatureClass
  pFeatureLayer.Name = pOutFeatureClass.AliasName
  pMap.AddLayer pFeatureLayer
End Sub