This should work.
Add the following custom properties on the popup.
mX (Integer)
mY (Integer)
On the mousePressed event of the popup, enter the following:
event.source.mX = event.x
event.source.mY = event.y
On the mouseDragged event of the popup, enter the following:
[code]
window = system.gui.getParentWindow(event)
mouseX = event.x
mouseY = event.y
windowX = window.getX()
windowY = window.getY()
window.setLocation(mouseX+windowX-event.source.mX,mouseY+windowY-event.source.mY)[/code]