UFN_VALIDHOURMINUTE

        create function dbo.UFN_VALIDHOURMINUTE(@HOURMINUTE nvarchar(5))
        returns bit with execute as caller
        as
        begin

            declare @HOUR smallint
            declare @MINUTE smallint    

            --4 chars are required
            if len(@HOURMINUTE) <> 4
                return 0

            if isnumeric(@HOURMINUTE) = 0 
                return 0

            set @HOUR = cast(left(@HOURMINUTE, 2) as smallint)
            set @MINUTE = cast(right(@HOURMINUTE, 2) as smallint)


            --Validate that the time is between 0000 and 2359

            --Hour must be between 0 and 23
            if @HOUR > 23
                return 0    

            if @HOUR < 0
                return 0

            --Minute must be between 0 and 59
            if @MINUTE > 59
                return 0    

            return 1
        end