How do I open a Firefox browser window, and only a Firefox browser window, from within Access 2003 using VBA?

My company has a web page that not only works best, but on some platforms works only, with Firefox. My access 2003 project needs to access that web page but the code I'm using opens Microsoft IE by default. How do I access that page with Firefox, no matter what default browser is set on any given PC? It needs to be a user-interactive browser page, not just data retrieval from the web page, so just opening a browser window is all I need.

Code:
Dim urlData as String
Dim urlHTTP as String
Dim DataList as String
Dim browser as SHDocVw.InternetExplorer        'This is probably where I need to start changing my code?
Dim objVph, objBrowserPage as DataObject
...
DataList = {search term... calculated earlier}
Set browser = New SHDocVw.InternetExplorer
urlData = "http://.../processRequest?HTMLVersion=5.0&loc=en_US&tracknum=" & DataList
browser.navigate (urlData)
browser.resizable = True
browser.Visible = True
...