Henry -- Thanks for your help and guidance. I am still not 100% sure that my problem is solved. I think I can only check IApplicationInfo.ApplicationCode.Optomising to check to see if I am in non-interactive mode at the time. I cannot make it not need a interactive window with that property (I think...

I have cloned Trendlines_Automatic and modified it (slightly) to would as signal. It basically works in the when plotting on an interactive (graphic) instrument analysis window. However, I would like to use it in Portfolio Backtester, with no graphic. When I try, it comes up "invalid pointer", I ass...