declare @i int
exec sp_executesql N'select @i = 999', N'@i int output', @i output
select @i


-- setting output parameter from dynamic stored procedure call

declare @OutputParameter varchar(100) ,
        @error int ,
        @SPName varchar(128) ,
        @SPCall nvarchar(128) ,
        @rc int
select @SPCall = 'exec ' + @SPName + ' @OutputParameter output'
exec @rc = sp_executesql @SPCall, N'@OutputParameter varchar(100) output', @OutputParameter output
select @Error = @@error