When i render LC and irr at 4 am and then switch to the rgb pass, sometimes when redbull,coffe and pils are not doing the trick anymore I do tend to forget to switch that button off. 
So a small popup would do the trick for me once I hit render.
Ralf
Deadline has a few nice bits like this when you submit a render - it gives you a list about things like file names for output not being set, files / folders being wrong and so on - might be worth a look since they give you a free 2 computer license of it!
You can save the following as a script and then load it into the “Pre-render” script slot of the Render Setup dialog. Save a blank scene with this set as your maxstart.max file and it’ll always be there. Also check “Execute locally” so it doesn’t mess up any backburner servers.
if renderers.current.options_dontRenderImage==true then messageBox "V-Ray Global Switch \"Don't render final image\" is checked.\n\nFinal image will NOT be rendered!" title:"Warning"I don’t know a way to actually cancel the render via maxscript so it just puts up a warning-you’ll have to cancel the render yourself once you press “OK”.
That is enough for me great thanx