Set circular icon via script

I have a circular complication on my iWatch that displays the power generated by my solar panels. This all works well.
Because the text in the middle is so limited, I have code that displays the power as 3 digits when the value is below 1000 watts and as ‘d.d’ kilowatts when above.
What I’d like to do is to also change the icon (preferably as ‘W’ and ‘kW’) but it appears that the icon is fixed - at leat in the UI that defines the complication.

Is there are way to set the icon in the script that displays the value?