Yes, it's possible. Hopefully, this should keep you going:
Code:
<script type="text/javascript">
window.onload=function(){
document.getElementById('opt').onchange=function(){
document.getElementById('myframe').style.height=this.value+'px';
}}
</script>
<select id="opt">
<option selected="selected">Change IFRAME height</option>
<option value="300">Change IFRAME height to 300px</option>
<option value="500">Change IFRAME height to 500px</option>
<option value="1000">Change IFRAME height to 1000px</option>
<option value="100">Change IFRAME height to 100px</option>
<option value="50">Change IFRAME height to 50px</option>
<option value="150">Change IFRAME height to 150px</option>
</select>
<br><br>
<iframe src="http://dynamicdrive.com/forums" id="myframe" style="border:0px;width:100%;"></iframe>
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