PopPlanner is a GUI program to interactively construct ms and msms command lines. Currently it is distributed as executable jar file. You can download it here:
You will need java installed and it has been tested on windows, macs and Linux. In many cases simply double clicking the jar file will run it, however you will get warning dialogs about trusting the code. I assure you it does nothing nefarious.

If double clicking does not work, you can run the program from the command line as follows:
java -jar PopPlanner.jar
This assumes java is in the path.

Using the program should be fairly easy by just playing around with it. You can also just paste existing command line into the program as well.

The source is available on request. Eventually a github page will be set up.