Call a Function

Hi

I created a GUI-STATUS using se41 and added it in my abap report:

start-of-selection.

set pf-status 's001'.

I also added an icon in the GUI-STATUS to use for calling a function 'ALVG', now, where do I add the code that will execute this function, is it in SE41 or in the report itself? I also tried modifying screen 1000 but got an error message that this screen should not be modified.

Need some advice on this one, thanks!