help with popup win

[mikaint]

I have a popup window and i need to apply navigation in this window...this is my script:

 

function win10(IMG,TITLE,DESCR,IMG2)
{
  var win = new Window({className: "alphacube", title: TITLE, width:785, height:500}); 
  win.getContent().innerHTML = "<img src='pressimg/" + IMG + "' /><br><div align='center' class='gold'><a href=\"javascript:win10('" + IMG +"','TITLE','DESCRIPTION','" + IMG2 +"')\" target='_self'>image 1</a> | <a href=\"javascript:win10('" + IMG2 +"','TITLE','DESCRIPTION','" + IMG +"')\" target='_self'>image 2</a></div><br>" + DESCR + "<br>"; 

  win.setDestroyOnClose(); 
  win.showCenter();
  win.setConstraint(true, {left:20, right:20, top: 30, bottom:10})
  win.toFront();
}

 

There are two pictures and two links to those pictures. The way i made it, it opens a new popup every time a link is clicked. This is normal as the script contains the following command: var win = new Window({className: "alphacube", title: TITLE, width:785, height:500});

 

What i want to do is to add an if statement that will somehow display the picture in the same window, but unfortunately i'm not that good with javascript so i'll need some help...