"as" for setwindow

The "as" option for the display function is helpful, but it seems like there is no way to modify it thereafter? I have a window hook that lets the arrow keys change what column is being displayed on a graph. I'd like to change the window title to show the index of the currently displayed column (without changing the window name), but I don't see a way to do so. It seems like setwindow/as="my new titleStr" would be a nice addition to allow this.