I have looked through some posts about screen, as my understanding, 1st, define a parameter with a user command, 2nd, in at selection-screen output, use loop screen to modify the screen, but how does it know which parameter it will trigger event for? if i define param1 with user command cmd1 and param2 with user command cmd2, how to control that? I found the "at selection-screen output" only trigger the param1, but if i also want to do it use param2, how to do that? i tried to use sy-comm = 'cmd1' to check, but there is no data in sy-comm, confused.
another question, can i use "at selection-screen on param1" to make the screen dynamic? seems not, only some form or function can be added there, but not changing the screen, right?
thanks for your help.