Getting the Wimp to ignore VDU output?

I have something that prints to a sprite on a callback.
The problem is, if this happens when the current application has finalised itself but is still busy and has not yet quit (ChangeFSI and WebSurf exhibit this), the Wimp helpfully notices the VDU activity and outputs “Press SPACE or click mouse to continue” when the program finally does exit.

Is there a way (legal or otherwise) of telling the Wimp that any VDU output it may see does not concern it and don’t be an ass? Because it looks like the Wimp hangs on to the WRCH vector without seeing if the output is redirected or otherwise.

My current way of dealing with this is:

• Are we in the Desktop?
• Is the current task handle &0?
  If the answer to both is yes, then inhibit.

I rejected issuing SYS "Wimp_CommandWindow", -1 because that may adversely affect something that might actually be using a command window.

I would just like to say, for the microsecond that my callback code runs for, “ignore this, it doesn’t concern you”.

Is it the Wimp’s exit handler that outputting that text? If so, a workaround might be to install your own exit handler whilst you’re outputting to sprite, which redirects output back to video if OS_Exit is called.