I'm hoping someone can help me write a function, please, please, please.

What I have:
I have a spreadsheet ($surveys) with one record per line.
The columns a
A1:Name (type:text)
A2:Survey1 (type:date)
A3:Survey2 (type:date)
A4:Survey3 (type:date)

What I need:
I need a function that tells me when a survey is due and when it's past due
for each person. Names and dates will be entered by hand. The function
needs to function like this:
If there is no date in Survey1, disregard that row.
If there is a date in Survey1, but not it Survey2 or 3, use Survey1's date.
If there is a date in Survey2, but not Survey3, use Survey2's date.
And if there is a date in Survey3, use that date.
(In other words, use the latest date.)
The date needs to be compared to Today's Date and the words "Survey Due" or
"Survey Past Due" needs to be returned. "Survey Due" needs to be returned if
after 70 days and "Suvey Past Due" if after 90 days.
I then need this list to be truncated (all the blank cells removed) and
displayed with corrolating names on another speadsheet ($surveys_due).

What I'm after:
Surveys need to be completed every 90 days for each person. What this
function should do is give me a list of people who are due or past due to
take the survey no matter if it's the first, second, or third survey they've
taken. It's a "tickler" to let me know when to get folks in to take their
next survey and when they're past due. I'm not interested in those who
haven't done a survey. (I realize that this does not give me consecutive
dates for each next survey, every 90 days down the line. The "next" survey
should come after 90 days of the previous one; in other words I don't need
them to be every 90 days consecutively from the first one, 90 days does need
to pass between them no matter how long it's been between the previous 2
surveys.)

Can anyone please help me with this?

Thanks for your help in advance.
- Dax