Dynamic compositefields

[rbastic]

Hello all,
I am having what I believe to be a simple problem with ExtJS compositefields and yet the solution is evading me.

If I have a compositefield with 3 simple fields inside of it, and I'd like to replace the 3rd field dynamically (when a combobox value changes) and have the window re-layout using .doLayout() or some other construct.... How can I do it? I tried manually modifying the .items arrays with the necessary dynamic field (inside a combobox select event) and then calling .doLayout() on the window itself, but it doesn't work.

Is there a better approach, or simply one that does what I need?

Thanks in advance. I can possibly post additional code samples if this is not enough.

// Some sample code (incomplete)
				globals['broadcast_win'] = Radius.makeWindow({
					title: 'Broadcast Change',
					width: 620,
					height: 350,
					items: [
						{
							xtype: 'compositefield',
							items: [
								RT.makeLabel('Changes'),
								RT.makeTextArea({
									id: 'filters',
									name: 'filters',
									autoScroll: true,
									readOnly: true,
						            width:275,
						            height:100							
								})
							]
						},
						{
							xtype: 'compositefield',
							id: 'source_composite',
							name: 'source_composite',
							items: [
								RT.makeLabel('Source:'),
								fieldCombo1
								, opCombo
								, RT.makeLabel('Value:')
								, srcValue
								// (value), changes dynamically!
							]
						},
						{
							xtype: 'compositefield',
							id: 'target_composite',
							name: 'target_composite',
							items: [
								RT.makeLabel('Target:')
								, fieldCombo2
								, RT.makeLabel('Value:')
								, destValue
								// (value), changes dynamically!
							]
						},
						RT.makeHtml('* All values are case-sensitive.<br>'),
						RT.makeHtml('** All broadcast change rules are combined using "AND" conditions.<br>')
					],
					buttons: [
						new Ext.Button({text: 'Add', handler: bcAddHandler }),
						new Ext.Button({text: 'Remove', handler: bcRemoveHandler }),
						new Ext.Button({text: 'Broadcast', handler: broadcastHandler }),
		    			new Ext.Button({text: 'Cancel', handler: broadcastCancelHandler })
					]
	    		});	    		
	    	}

	    	globals['broadcast_win'].show();

[rbastic]

It really just comes down to replacing individual elements on a page dynamically. Doesn't necessarily have anything to do with 'compositefield' ....

Anyone have any thoughts?