Error calling PO Dispatch App Engine from PeopleCode

I'm trying to dispatch a PO from an App Package using CallAppEngine and am getting this error message.

ErrorReturn-> 164 - Function '%OutDestType' cannot be run on the application server. (180,164) PO_DISPATCH.PO_Dispatch_Print.OnExecute Name:dispatch PCPC:1153 Statement:25

I am not sure if I should and how I could specify the Output Destination Type with CallAppEngine.

Has anyone run into this problem?

Here is my code:

&stateRec = CreateRecord(Record.PO_DISP_AET);

&stateRec.OPRID.Value = %UserId;

&stateRec.RUN_CNTL_ID.Value = "PS_PO_DISPATCH_DEFAULT";

&stateRec.BUSINESS_UNIT.Value = &bu;

&stateRec.PO_ID.Value = &po_id;

&stateRec.EMAIL_DISP.Value = "Y";