Nope, postable commands cannot be run more than once as far as I’m aware, so looping will not work I’m afraid. In fact, I don’t even think you can daisy chain them in the Dynamo graph, although I haven’t tested thoroughly as I try to avoid Postable Commands if I can.
Perhaps you could use the TransactionManager.Instance.ForceCloseTransaction() and put the transaction in your loop rather than outside but I think this will also fail.