问AppActivate并不总是激活应用程序窗口

EN

    'fuction to set the application active and then send keys 
    Function mySendKey(sKey,sTime)
       for i=0 to 600        ' this loop will continue about 30 sec if this not enough increase this number
        'get the window title of the IE
        title= sh.Exec("cmd.exe /c tasklist /v /fi ""imagename EQ iexplore*"" /FO LIST | FIND /i ""window title:"" ").stdOut.readline
        title= Mid (title,15,len(title)-14)
        sh.Popup  title,1

        Sh.AppActivate title
        Rtn=Sh.AppActivate(title)     '  window title of application
        If Rtn = True  Then           'if the window active then execute sned keys
            Sh.SendKeys  sKey                                     
            Exit For 
        End If
        wscript.sleep 10                              
      Next
     WScript.Sleep sTime*1000
    End Function

  'hide the cmd window from popup 
  If StrComp(right(WScript.FullName,11),"wscript.exe",1) = 0 Then    
  WScript.Quit CreateObject("WScript.Shell").Run("cscript.exe //nologo """ & WScript.ScriptFullName & """", 0, False)
  End If 
  'open internet explorer   
Set Sh = CreateObject("WScript.Shell")
Sh.Exec "C:\Program Files\Internet Explorer\iexplore.exe"
WScript.Sleep 7000
 'call mySendKey function to send keys to IE  
 Call mySendKey("(% )(x)",1)                         'max the windows of IE
 Call mySendKey("({F6})(www.yahoo.com)    (~)",10)   'browse to yahoo and wait 10 sec to load
 Call mySendKey("({F6})(www.msn.com)      (~)",10)   'browse to msn and wait 10 sec to load 
 Call mySendKey("(% )(C)",1)                         'close the IE