SQL Fiddle:http://sqlfiddle.com/#!6/9eecb7d/1607
declare @a nvarchar(32) = 'àéêöhello!'
declare @b nvarchar(32) = 'aeeohello!'
select case
when (cast(@a as varchar(32)) collate SQL_Latin1_General_Cp1251_CS_AS) = @a
then 0
else 1
end HasSpecialChars
select case
when (cast(@b as varchar(32)) collate SQL_Latin1_General_Cp1251_CS_AS) = @b
then 0
else 1
end HasSpecialChars
(въз основа на решение тук:Как мога да премахна акценти върху низ?)