I thought I'd done this before, but perhaps I haven't.  The batch is empty. I've confirmed that.  But the below doesn't delete it and the retval doesn't return an error.  Am I missing something?  I've confirmed that sBatchNo has the correct batch number value (which is a 5-digit number).

retVal = oAPInvoice.nSelectBatch(sBatchNo)
retVal = oAPInvoice.nDeleteBatch(sBatchNo)

Any ideas are much appreciated!