That is not a (IMHO) good way of doing that. You want to get the element and set the property in JS, not use JS to write out the value.
Give the div an ID, and use
document.getElementById('theID').style.height = divh + "px";
If anyone knows of a website that can offer ColdFusion help that isn't controlled by neurotic, pedantic jerks* (stackoverflow.com), please PM me with a link.
* The neurotic, pedantic jerks are not the owners; just the people who are in control of the "popularity contest".