Ajax Rest and Soap calls conception problems

Hi everybody,

I met a problem, maybe a misunderstood, about ajax rest and soap on CRM 2011.
Explaination :

I try to develop a little web page with a javascript function call on ribbon button click, this function is not very complexe, here the algorithm :

begin
	get CurrentCampaignRecordGuid
	RetrieveMultiple(linked listSet) // Ajax call synchronous. In my case linked list are dynamic
	foreach
		RetrieveMultiple(Fetch) // SOAP call synchronous 
		Count ListMember
	end foreach
	display countTotalMember
end

So my probleme is simple, thats work perfectly with synchronous call but the query can be long and because its synchronous my page is freezed.
So as AJAX stand for Asynchronous, I tried to pass this process on asynchronous mode and to display a loading bar to the user :
- On asynchronous my function finish before the end of all the asyncprocess, so the loading bar is immediately finished
- On asynchronous, I know its possible, but I dont know if its recommanded to call SOAP asynchronously

I need your help to unblock me on those points, what can you suggest me about this kind of process ? Synchronous Asynchronous ?

Thx a lot for your time

Kya