C_TEXT($callback;$in;$out;$error)

$filename:=Select document("";"";"";Alias selection +Use Sheet Window )

If (OK=1)

$path:=DOCUMENT

If (Substring(Get 4D folder;Length(Get 4D folder))=":")  `Is Macintosh

$colon:=":"
$forwardslash:="/"
$space:=" "
$escapedspace:="\\ "

$path:=Replace string($path;$colon;$forwardslash)
$path:=Replace string($path;$space;$escapedspace)

$system:=System folder(System )
$currentvolume:=Substring($system;1;Position($colon;$system)-1)
$targetvolume:=Substring($path;1;Position($forwardslash;$path)-1)

If ($currentvolume=$targetvolume)  `Is Macintosh HD

$path:=Substring($path;Position($forwardslash;$path))

Else 

$path:="/Volumes/"+$path

End if 

$callback:="open "+$path

Else   `Is Windows

$colon:=":"
$system:=System folder(System )
$currentvolume:=Substring($system;1;Position($colon;$system))

$callback:=$currentvolume+"\\WINDOWS\\explorer.exe \""+$path+"\""

End if 

LAUNCH EXTERNAL PROCESS($callback;$in;$out;$error)

End if