To Set Iframe Height Dynamically

Question

I have to Set Iframe  Height Dynamically using Jquery or Javascript . I am Using following jquery  code:  
 var theFrame = $("#IframeId", parent.document.body);
theFrame.height($(document.body).height);
My Problem is that data in iframe has some Images,video thumbnail which are coming from diffrent server Amazon,flicker (means from Cross domain). It takes time to load. So Iframe Height is not Set Exactly .
how can i set Exact height of iframe???????