Chain Selection – Chain Number to Modifier

In a Device Parameter Mapping I would like the *Chain Targeting>Chain Number* to be controller by a Modifier (See Attached Screen Shot)

I would like this modifier to output the chain number of the currently active/selected chain in Ableton.

I have attached the current iteration of my script to try and achieve this, I feel like I am close but can’t seem to find the ‘active chain’ condition.