Support for multiple browsers in a single test

We have a project that needs to run end to end tests sequentially, but on a different browsers.

We have created separate sub-test case for each scenario that needs to open in another browser, so we call them:

Global.DoInvokeTest('%WORKDIR%/CallCenter', params);    // This runs in Chrome
Global.DoInvokeTest('%WORKDIR%/ApplicationConsole', params);    // This runs in IE

first thing that these tests call is a function (in user-defined library) that determines in which browser and environment they run in:

function selectEnvCallCenter(url) {
    Navigator.Select('Chrome');
    Navigator.Open(url);
...

function selectEnvAppConsole(url) {
    Navigator.Select('IE');
    Navigator.Open(url);
...

Invoking the sub-tests works in the main test file, but if we try to invoke these from a sub-test, it opens all (sub-)sub-test files in the same browser and doesn't change browsers...