How to close rosgscreen using onkeyevent() in scene graph xml ?

I am using screen.Close() method in the while loop. is this correct way i am doing ? and how to access the data from brs to xml scene??
ex: m.global.setField("tempmessage", "Are you sure you want to Signout?") I want access  this "tempmessage"  value in the ConfirmSignout.xml.
could you please help me on this..

Main.brs

sub ConfirmSignOUT() As Object
    screen = CreateObject("roSGScreen")
    m.port = CreateObject("roMessagePort")
    screen.setMessagePort(m.port)
    m.global = screen.getGlobalNode()
    m.global.id="GlobalNode"
    m.global.setField("tempmessage", "Are you sure you want to Signout?")
    scene = screen.CreateScene("ConfirmSignout")
    screen.show()
    while(true)
        msg = wait(1000, m.port)
        if(scene.visible = false)
          screen.Close()
          return Invalid
        endif
    end while    
End sub

ConfirmSignout.xml

<component name = "ConfirmSignout" extends = "Scene" >
 
  <script type = "text/brightscript" >
 
    <![CDATA[
 
    sub init()
print "m.top";m.global.id
m.top.backgroundURI ="pkg:/images/rsgde_bg_hd.jpg"
dialog = createObject("roSGNode", "Dialog")
dialog.optionsDialog = false
dialog.title = "Alert"
dialog.message = m.global.tempmessage
dialog.buttons=["No","Yes"]
dialog.visible = true
m.top.dialog = dialog
end sub

sub dismissSignoutdialog()
m.top.dialog.close = true
m.top.visible = false
m.top.backExitsScene = false
end sub

    function onKeyEvent(key as String, press as Boolean) as Boolean
handled = false
button_val = m.top.dialog.buttonSelected
if not press then
if key = "OK"
if(button_val = 0)
dismissSignoutdialog()
return true
else if (button_val = 1)
print "m.top";m.top
'return true
end if
else if key = "back"
m.top.backExitsScene = false
end if
end if
      'return false
    end function
  
    ]]>
 
  </script>
 
  <children >
 
    <Label
      id = "SignoutLable" />
 
  </children>
 
</component>