You can use the FolderItemLaunch command to launch an external program both under OS X and Windows platforms
FolderItemLaunch fhandle,value
This command launches the application specified by the given file handle. If value is zero then the application will run in the background, and if non zero will run in the foreground.
Place the following script in a button to launch a file called Photoshop.exe in the given directory:-
Local fname,fhandle,fdetails,ftypes, fpaths,fnames,fextens
@ set the filename of the program to launch
Put 'C:ProgramFiles\Adobe\AdobePhotoshop.exe' into fname
@ Get the file handle
FolderItemGetAbs(fname,fhandle,fdetails,ftypes, fpaths,fnames,fextens)
@ Launch the application in the foreground
FolderItemLaunch fhandle,1
I'm sorry the above script looks messy but the FolderItem command is very flexible and returns so lots of info.