Variable scope in brightscript

MainScene file:

<?xml version="1.0" encoding="utf-8"?>
<component name="MainScene" extends="Scene">
    <script type="text/brightscript" uri="MainScene.brs" />
    <script type="text/brightscript" uri="pkg:/components/UI/ScreenStack.brs" />
    <script type="text/brightscript" uri="pkg:/components/UI/HomeScreen.brs" />
    <children>
        <Spinner />
    </children>
</component>

MainScene.brs: 

function init()
    m.top.backgroundUri = ""
    m.top.backgroundColor = "#0E1420"
   
    m.screenStack = []
    InitScreenStack()
    ShowHomeScreen()
end function
...

I have a HomeScreen component, when user click in "Channels" i want create component and add in ScreenStack
HomeScreen.brs:

...
...
sub updateFocus()
    for each key in m.borders
        m.borders[key].opacity = 0
    end for
    m.borders[m.currentFocus].opacity = 1
end sub

function onKeyEvent(key as String, press as Boolean) as Boolean
    if press then
        nextFocus = invalid

        if key = "OK" then
            ClickButton(m.currentFocus)
            return true
        end if
        ... 
        ...
        ...
        end if
        
        if nextFocus <> invalid then
            m.currentFocus = nextFocus
            m.buttons[nextFocus].setFocus(true)
            updateFocus()
            return true
        end if
    end if
    return false
end function

function ClickButton(button as String)
    print "ClickButton: "; button
    if button = "channels" then
        m.CatagoryChannels = CreateObject("roSGNode", "ChannelsCategory")
        ShowScreen(m.CatagoryChannels)
    end if
end function

ShowScreen(m.CatagoryChannels) don't exist in this scope.

How i can resolve it?