Calling a Screen as a Modal Dialog

Hi

I have created a 'Z' Transaction which has only one Screen which is of type 'Modal Dialog'. Whenever i run the Z Transaction, i get the screen in a full window size. Is there any way by which i can restrict this screen to a Modal Dialog. I know that we can use call Screen XX Starting at .. Ending at.. Option. But this will help me only when i have two screens.

Can anyone answer this as it is urgent !!!

Rgrds,

Murli.