Hey Paul,
	To use SetWindowTitles_ the syntax is:

SetWindowTitles window_ptr, window_name, screen_name    <- note: may need brackets :|

Either window or screen name can be NULL (which the ROM Kernel Reference Manual Libraries) 
says that it will be returned to DEFAULT.
Either may also be -1 which means it is UNCHANGED.

To get the window pointer - how is it now?. Something like:
window_ptr.l=Peek.l(Addr Window(win_number))

		Simon

P.S. Don't quote me on it not using memory like WTitle but it appeared not to! Why?
Well I made a window title bar display the current time and with WTitle, each second used 20% of 1k 
and only freed it when my program terminated. 
I then used SetWindowTitles_ and it uses 20% of a 1k, but keeps freeing it so actually using no more 
memory than it should. Hurrah. :)