Screen events using screens

Hi gurus ...

I made an ALV report that has a selection criteria (scr 1000).After the alv is displayed i have a button in my gui that calls a screen (200) .My problem is that when i run the report the Fisrt time i can navigate through the screen and i can see my data (alv) .The second time that i try to navigate to my alv i can't and always i go to the screen .

Look how my report goes :

run -> scr 1000 -> data (alv) -> scr 200 -> <b>scr 1000 -> scr 200 -> scr 1000 -> scr 200</b> etc etc

The problem is that i can\t see that data again .

Please can someone explain me the logical series for navigating throu screens ...

Please help ....