Setting up custom lists

I need some guidance on how to set up a custom list in the web interface. After selecting “custom list”, with every type of list i have tried, I get the message ‘error: Please use field(‘C’) to access C because it starts with an upper case letter.’
What is the correct format of a list? My data specification calls for one of “COL”, “MAR”, “NONMAR” etc
UPDATE
OK. It is now returning the error with all types (GUID, Dates, etc) but the first formula

SOLVED.
It needs an id or it crashes with that strange error message :frowning: