SQL Server: An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause

HI

I wrote below SP

ALTER procedure [dbo].[viewSpecialReg]

as
begin

select (select Name from S_register) as Name,(select Behcode from Behcode where date=MAX(date)) as behcode


end

but this error happen

An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference.