Well, not really useful, since it doesn't support brackets.

Draft send by Rajganesh on the other hand doesn't support decimals. (of course, I can force it)

Don't have time right now to provide mine solution, but for this script to be useful it should works as follows:

select dbo.EvalSQLStatement('(5 * 3 + 1) / 3')

-- result should be 5.333333