The expression tool can be taken even further.
If you want to input some function that requires input from two separate model runs, this can be achieved with a simple specifier.
First you need to input a cell array of model files in the modfil input, the order of this is important.
Then, (for example if we were comparing water level between two runs with different bathymetery), we specify our variables with M1. or M2. beforehand.
'M1.H - M2.H' will subtract the water level of the second model in the model cell array from the water level of the first model.
This has the same limitations of normal expressions, therefore at this stage it is not possible to do these comparisons on models with different numbers of cells.