Viewport problems.. how to load a window in the center region in viewport

[farout]

hi...
how can i load my window to my center region in viewport

and my second problem is when clicking on the Visitor List button loads or show the form and clicking the Visitor List button a second time makes the form disappear. Any reason it would not reload itself?

My viewport

var viewport = new Ext.Viewport({
layout: 'border',
renderTo: Ext.getBody(),
items: [{
		region: 'north',
		xtype: 'panel'
		,title: 'TEST'
		,tbar:[{
				xtype: 'tbspacer'
			},{
				xtype: 'tbbutton',
				text: 'Visitor List',
				handler: function(btn){
					winvisitorlist.show();
				}
			}
		]
		},{
			region: 'center',
			xtype: 'panel'
		}
		,{
			region: 'west'
			,xtype: 'panel'
			,width: 200
			,title: 'Message'
			,split: true
			,collapsible:true
		}]
});

my window

var winaddvisitor = new Ext.Window({
	title: 'Visitor List',
	id: 'helpwin',
	width: 300,
	height: 300,
	modal: true,
	tbar: [{
		text: 'Add Visitor',
		handler: function(){
			winaddvisitor.show();
		}
		},{
			text: 'Disable',
			handler: function(t){
				t.disable();
			}
		}
	]
});

thanks

[Condor]

Your visitor list shouldn't be a window at all.
- Change visitorlist to be a panel.
- Make your center region layout:'fit' (or 'card').
- add() visitorlist to the center region and call doLayout.