Setting iFrame height programmatically

In Dynamics CRM, how do you set the height of an iframe programmatically? The following function doesn't do anything, the iframe always comes up the same size. Even when you go to iframe properties and change the row numbers there, it still doesn't cause any changes in size.

function doOnLoad(sender, args) {

        setIframeHeight();

}

function setIframeHeight() {

    //lowest control in iframe

    var element = $('btnInsert');

    //the following line gets called, and what's displayed is 25

    alert(window.parent.parent.frames[0].document.getElementById('IFRAME_TransactionProduct_RA_d').parentNode.height);

    //the following line doesn't do anything        

    window.parent.parent.frames[0].document.getElementById('IFRAME_TransactionProduct_RA_d').parentNode.height = 500;

}