I use Zoho as a tracking mechanism for international shipments.  A lot of the tracking has to do with dates - e.g. ETA west coast, ETA final destination, ETA delivery, etc.  What is the syntax for the null "if ETA west coast = null" send email?  Does the "null" in the code need to vary depending on whether the field is a string, numeral, multi-select, etc.?

Another question I have is that since my tracker has a lot of date fields, I would like to be able to say "if today is between date-entered-in-tracker and three-days-prior-to-date-entered-in-tracker send an email."  What is the syntax for something like this?

Last thing - there are options in the script for almost every type of trigger - e.g. load, success, etc. - but what I really need is for the form to check once a day.  Is this possible?  In the case of the above scenario, I don't want an email every single time I access my database where today falls within a date range - just one in the early afternoon as a friendly reminder.  

Thanks in advance for any helpful responses!