Using the A6 templates, it's fairly simple to create a door.

Create a new Template Script for the level (_A6_template_project), and then (if your door is already a map entity) select the "door" action from the behavior list.

Hope this helps.

Code:
void main()
{
    cout << "I am MrCode,";
    cout << "hear me roar!";
    system("PAUSE");
}