Index on wide varchar column

Hi all,

I'm working on an application that needs to use a big table (millions of
rows). This table has around 70 columns, one of which is a
VARCHAR(30000) that is used exclusively to sort the rows in a specific
order. The application runs in batch and reads every row of that table.
Are there any restrictions about using such a wide column to order a
table? Can an index on that column help?
Any help will be greatly appreciated.

Regards,

Antonio Sergio