If you want to use LabView to programmatically close another application, you can use VIs from WinUtil.llb, which you can download from NI by clicking here [broken link removed].
Look at an example like Maximize Window.vi. If you pull down the list on the diagram that's set to Maximize Window, you'll see Quit Application. This VI takes as an input either the window refnum or the window name (from the title bar).
