Assembler: Measurement across sweep vs leaf values

Hi,

I am familiar with calculation across corners or across sweep, but I wonder about one thing:

I have one output, and run a sweep of VDD. To get the difference of the output CalibratedGain from run with 2.4V and 5V I can get a correct plot with this calculator expression:

leafValue( CalibratedGain "VDD5V0" 2.4 )-leafValue( CalibratedGain "VDD5V0" 5 )) => nice plot

I can then push this expression to the ADE output sdetup, but then a re-evaluate gives me an error.

Can I improve to avoid the error or use an expression vs sweep instead?

Bye Stephan