g_signal_connect (data_store->dict, "variable-inserted",
G_CALLBACK (on_variable_inserted), data_sheet);
g_signal_connect (data_store->dict, "variable-deleted",
g_signal_connect (data_store->dict, "variable-inserted",
G_CALLBACK (on_variable_inserted), data_sheet);
g_signal_connect (data_store->dict, "variable-deleted",