Concatenating contents of selected cells or a range into single cell.

Hi. I need to combine contents of selected cells or a range into single cell with separator "/" while ignoring duplicate values (if whole string in cell is repeated); for example. Notice the range corresponds with the day of the week. Concatenation method suggested by Chandoo.com does not seem to work on my excel 2007 with error. Moreover does not fully solves the problem.

Can anybody suggest a formula or VBA macro to solve the problem? Currently I am doing it mannually and its really tedious work. Thank you.