'Erev_estimator' is a software for PC (no Mac version, sorry Clair), with which the user can change the value of any parameter affecting Erev_ANT and/or Erev_ATPase, and observe how are the A (green), B (orange), C (grey) and D (brown) spaces altered. Below you can see a screenshot of the software.
'Erev_estimator' can be downloaded here, as an exe file (Chrome browser may warn you that 'Erev_estimator is not commonly downloaded and may be dangerous', and prompt you to discard the file; click on the arrow and choose "Keep"). Other browsers will also warn you, just do what it takes to keep the file.
Instructions for using Erev_estimator can be downloaded here.