Initialize combo on form with server side filtering

I would like to use combo on a form with filtering (server sends data limited to 20 records when user types characters).
The structure of combo is initialized with json string :

{type:"combo", name:"mycustomer", serverFiltering : "customers.php",filterCache:true,filterSubLoad:true.....}

Form is filled with data using load with XML request.
When I type characters in combo it works fine and I can save the value selected … but when I go back to the form I can’t get the label of the option selected (and customers.php is not called).
I suppose the solution should be to call customers.php and to get back the value and label with selected option set to true.
That’s the idea but I don’t know how to do this.

Thank you for you help

May be I need to explain my problem differently.

I would like to use a combo on a form.
The form is loaded in 2 steps, the structure (json) and then the data for the fields.

Combo should use a big database with server side filtering.
It means that all options can’t be loaded and the list displayed to the user is limited to something like 20 options (the first 20 corresponding to the characters typed in the combo).
I have got no problem with combo structure and the selection (filter) in the combo works fine.
I can also get the value of combo to save it.
My problem is “only” to load the initial text (what should be a standard thing when doing CRUD operations with large dababase).
In my case, the option to load is known only when the value of the combo is set.
The easiest way would probably be something lile a subname for text of the optio n when loading data or call to the filter URL with specfic indicator when data of combo is loaded.

Iideas…and solutions are welcome.

Sorry I can’t give a demo since I don’t know how to process.
I have gone through the documentation for hours

I apologize for the delay with the reply.
The problem is confirmed. We’re working on a solution.

I found a workaround using the callback function after loading data in form.
It looks like :

myForm.load("formdata.php,function() {

selected is a flag to specify the mask is an id and not a search string.
combodata.php is the value of serverFiltering attribute of combo in the form.
It works even it is not really nice.

I have the same problem with combo in lightbox (I made a post for this on the scheduler section of this forum).
But in this case I don’t know to access the combo or the form object of lightbox to apply the getCombo function.
So no solution yet …