Ajax and Preloads and List Selection

Hello

I know what i would like to do but i don t know how to do that in C2...

I get a server response and fill some information in a list (the list contains the list of levels available)

=> Fired on start of layout call a server, when reponse is success, this call a function.

=> Fired On call of the function AND There is a loop to populate the list

The player choose the level he wants to play

=>Fired by on selection changed

I would like to preloads few sound needed for the next layer

=>Fired by Audio all preloads complete

I would like all theses actions are done, to set visible the button witch permits to go the the next layer.

How can i wait until all is done?

I look for a answer in the manual and i found only that :

https://www.scirra.com/manual/75/how-events-work

This link mention multiple condition but not with a loop.

I think i could do that multiple condition by setting a flag but i ll set this flag n times in the loop... that seems so strange to write that...