Wsing WSHPipe I was able to check and see if my PST file was open.

Code:
 
break on



$output=wshpipe('openfiles /query',1)
for each $line in $output
  if instr($line,"pst")
    ? $line
  endif
next

Function WshPipe($ShellCMD, OPTIONAL $NoEcho)
	Dim $oExec, $Output
	$oExec = CreateObject("WScript.Shell").Exec($ShellCMD)
	If Not VarType($oExec)=9 $WshPipe="WScript.Shell Exec Unsupported" Exit 10 EndIf
	$Output = $oExec.StdOut.ReadAll + $oExec.StdErr.ReadAll
	If Not $NoEcho $Output Endif
	$WshPipe=Split(Join(Split($Output,CHR(13)),''),CHR(10))
	Exit($oExec.ExitCode)
EndFunction