Copy IDOC outbound file to the Subsystem

How do I get the Name of the last file generated by SAP in a Idoc Outbound process.

I Need to pass that file name to the command file (.bat) specified in Outbound trigger option of the WE21 SAP command.

I need to copy the last file generared by IDoc Sap to the Subsystem through a Copy command inside the Command file.