Async process to refresh mashup

Hi,

I have a iFrame widget which shows webGL 3D model returned from external system. There is a button on the mashup to send post request to the external system. I want to make visible = true for the iFrame only after external system responds.

What I did;

- Made async service to post request to the external system.

- The service wait until the external system responds

- The service set session parameter to true after the external system responds

Problem;

- Session parameter is not updated by the async service

Any other solution?