Excellent! That works nicely, but in general (AR_OpenInvoice was an example) - how would one know which UI name to use?
Side Note: while this worked for 'AR_OpenInvoice_bus', it didn't work for 'AR_InvoiceHistoryInquiry_bus' using 'AR_Customer_UI' for the LookupTask() as in your case. Oddly, I received successful return codes using 'AR_InvoiceHistoryInquiry_UI', but the data didn't change. Using 'AR_Customer_UI' a retVal of 0 was returned.