How to test if form exists

I create instances of shared forms using createNewFormInstance. I need to dynamically change properties of elements on these forms. In order to do this I need to know if the form has been instantiated at that point.

I suppose this also applies to forms created in the designer as well, for example, does a form exist in an included mode. Is there a way to tell if a form exists?

From the top of my head:

if(forms.formname)
{
     // Do this....
}

Thanks - that was easy.