Accessing viewstack problem

Hello communitie

hope anyone can help me.

I have a custom component with a TextInput with a id="userID" assigned.

and i have a Login button with a id="loginBtn" and have <s:Button id="loginBtn" includeIn="Login" x="318" y="237" height="20" label="Login" click="FlexGlobals.topLevelApplication.gotoView();"/>

In the main application i have this

public function gotoView():void {

                parentStack.selectedChild.label;

            }

<mx:ViewStack id="parentStack" width="1280" height="768">

    <s:NavigatorContent width="100%" height="100%" label="Login">

        <forms:MainSiteForm horizontalCenter="0" verticalCenter="0">

        </forms:MainSiteForm>

    </s:NavigatorContent>

    <s:NavigatorContent width="100%" height="100%" label="Admin">

        <s:ModuleLoader url="views/Administrator.swf"/>

    </s:NavigatorContent>

    <s:NavigatorContent width="100%" height="100%" label="Sales">

    </s:NavigatorContent>

    <s:NavigatorContent width="100%" height="100%" label="Designers">

    </s:NavigatorContent>

    <s:NavigatorContent width="100%" height="100%" label="Retailers">

    </s:NavigatorContent>

</mx:ViewStack>

Can someone help me with this please????

example if i type Sales in the TextInput userID and click the Login button i want to switch to that view in the main application.

any help will be really apreciated