Hi Maria,

I was thinking of doing something like this by using an external function that connects to a gui over sockets.

There is an example here:
https://github.com/adamLange/modelicaSocketExample

In the example there is a python server, server.py.  An external modelica function connects to the server over a socket.  The python server is just taking to operands and returning the average value.  Following this same pattern you could add some widgets to the python server for whatever interaction it is that you need.

Another example that might be useful:
https://github.com/adamLange/podRunSim

Hope that helps,
Adam