Vidar,
You will need to know the name of the new window that you create after you create it. It depends on if you have a form manager in place or not. You can also get the _SCREEN.FORMCOUNT before launching your new form. Then you could get the name by using the following after you launch the form.
lnForms = _SCREEN.FormCount
DO FORM cformname
_SCREEN.FORMS(lnForms+1).SHOW()
This should work, but there are other ways to get it as well by call the name of the form with the SHOW().