It sounds as if you want an exclusive lock on the table while you are getting the max - you can't prevent another user from running the Max function specifically (as far as I know).
To get an exclusive lock use
SELECT 1 from [Table] WITH (TABLOCKX)
SELECT MAX([Column]) as test from [Table]
But not that other users could still query the table by using
WITH (NOLOCK)
or
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
[EDIT] - I've just seen the comment from Digimanus. Do not try to use Max to create a unique ID. Use an
Identity[
^] column or
uniqueidentifier[
^]