Custom workflow for course registration

Hi,

I have an assingment to create list where items are courses and when new item is created you can give max participant value. List and columns are ok. (max participants(integer), current participants(integer), open/closed(choice), all participants(text)

So this is what I want to do with workflow:

• When someone wants to join the course, person will click "Join course" button
• workflow starts and it will add +1 to 'current participants'
• workflow adds display name of person to column 'all participants'
• if 'current participants' is same as 'max participants' then course will change 'closed'

I can use SP designer with workflow 2010 so is this impossible?

I have possibility to use visual studio 2010 but i'm not very familiar with C# workflows.

My biggest worries are that

1. how to store all participants to one column (multiline text) with workflow
   
2. how to display participants column only to admin users.

Thanks for any help/suggestions.

Antti Astikainen