IRasterBandCollection pRasterBandCollection = (IRasterBandCollection)pRasterDataset;
IRaster pTempRaster = new RasterClass();
IRasterBandCollection pTempRasterBandCollection = (IRasterBandCollection)pTempRaster;
IRasterBand pBand = pRasterBandCollection.Item(3);
pTempRasterBandCollection.AppendBand(pBand);
pRasterLayer.CreateFromRaster((IRaster)pTempRasterBandCollection);