It is possible.... but requires a little coding by hand currently.
If you had a button with id="browsebtn" and a text field with id="textField"
You could add code like:
<script>
window.addEvent('domready', function() {
var el=document.getElementById('browsebtn');
el.onclick=function(){
window.SetUrl=(function(){
return function(value){
document.getElementById('textField').value = value;
}
})(this.id);
var kfm_url='../../../HTMLEditor/Editor/plugins/kfm/index.php';
var kfmwindow = window.open(kfm_url,'kfm','modal,width=600,height=400');
kfmwindow.focus();
}
});
</script>