Excel Not clearing from memory

We have an issue with the Excel.exe not clearing from the list of processes, but only on 64bit systems (Windows 7 and Server 2008).    32bit is fine

CREATE @Application of @Excel handle in EX-APP

 MODIFY EX-APP @Workbooks::Open ( ws-ltout-file ,0,0) 

     giving EX-WORKBOOK.

MODIFY EX-WORKBOOK @PrintOut()       

call "c$sleep" using "2"

# next line added, but no change in behavior

MODIFY EX-APP @DisplayAlerts = 0

MODIFY EX-WORKBOOK @Close()

DESTROY EX-WORKBOOK

MODIFY EX-APP @Quit()

DESTROY EX-APP

I've seen the following online, but I'm not sure how to code this in Acu.

System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)

obj = Nothing

Thank you for any assistance!