We have a number of external lights under Cortex control and I am generally pleased with the way that I have them running.
However, there is one thing that bugs me a little and I would appreciate some thoughts on how I might address the issue.

At its basic level the external lights are set to come on based on time and an external light level threshold, and then go off at a set time later in the evening.
This can be overridden in one of two ways: There is a manual override that we can use to leave the lights on when we are out for the evening, and a 'daybreak' control that turns the lights on at a set time in the morning if it is dark and someone is moving around downstairs - this deals with the 'leaving home in the dark' scenario in the winter months.
So far, so good - so what is the issue? It's quite simple really - at this time of year the lights will regularly switch on for just a few minutes when it finally gets dark enough during the operating time period just before they are due to switch off.

So my question is this, what is the best way to ensure that the lights don't come on in a fixed period (perhaps 15 to 20 minutes) just before they are due to go off anyway.
I've tried setting up a virtual lamp with the same turn on time and light level settings, but with a slightly earlier switch off time, but I can't work out how to link that to the real light.
I am using various enable/disable and mode settings to control the lights already.

Any ideas much appreciated. And in case anybody is asking 'Why?' it has to do with when the dog and I decide to go for his 'last thing at night' walk :-)