how to find clusterGroup index that contains specific RowLabels?

I have a matrix of 20500 genes with relative data (20500*550). I have a clustergram of this data : clustergram(gene_data,'RowLabels',gene_list,'ColumnLabels',specieslist,'Colormap',redbluecmap,'Cluster','COLUMN');

I need to find a specific clusterGroup containing a list of genes (rowlabels). For example , I want to find the index of the clusterGroup containing the genes ('ABC','BBB1','BBB2').