Sorry, why are you posting this in the Interactive Brokers forum when your response has nothing to do with Interactive Brokers?
My mistake and apologies. Did not notice it was in the Interactive brokers forum. Happy new year and good trading to all.
Has anyone answered your question yet? This can easily be done (as pre-programmable 1-click ordering) on many platforms like NinjaTrader, MultiCharts, and SierraCharts. They all offer API for IB. There are many YouTube videos on this specific feature. Check it out.
You can do this in MotiveWave (third party platform connected to IB). In the Trade Panel you could create an Exit Strategy to take off half your position at a certain point and then have your other half taken off further out. Not sure what you mean by let it run? But you could use a Trailing stop or just a target further out...