Editing Data in CL_SALV

Friends,

I am struggling and hoping you can help. I have been experimenting with the classes under CL_SALV trying to write an application that allows a user to update date in a table in the ALV. I have been looking at a lot of examples like this one:

[https://www.sdn.sap.com/irj/scn/wiki?path=/display/snippets/update%252ba%252bfield%252bfrom%252bany%252btable]

I have the whole application working but I cannot figure out how to make the cells in the ALV editable.

Can someone give me a hint?

Regards,

KB