Set extensionProperty value dynamically

Is there any way to do it or it is not possible to set extension property value dynamically?

I wrote a general externalTaskHandler. I want to set extensionProperty value of service tasks with value of the variables or businessKey. But it does not work with whatever expression I could think of. I tried ${businessKey}, #{execution.processBusinessKey}, ${variableName}, ${execution.getVariable(“variableName”) ,…