Using GREP for Address Formatting Varying Addresses

Question

I create pre-addressed wedding envelopes for my clients. They provide me with a list of their addresses in a word document, and I lay them out in InDesign with each page being one envelope. (So I can export as a pdf and print all 100 or so envelopes in one swipe.)
The problem is, I'm getting more and more requests for more dynamic addresses. For example, lets say they want something like this:
Mr. & Mrs. Smith
1 3 4 5   M A I N   S T R E E T
NEW YORK, NEW YORK
87996
Solution 1: Use Line Styles
For example:
Line 1: Style A
Line 2: S T Y L E  B
Line 3: STYLE C
Line 4: Style D
This would typically work, except sometimes the addresses have 4 lines instead of 3, making some addresses look like this:
Mr. & Mrs. Smith
1 3 4 5   M A I N   S T R E E T
APARTMENT - 7B
New York, New York
87996*
*hint: It thinks this is line 1 again.
Instead of the desired result:
Mr. & Mrs. Smith
1 3 4 5   M A I N   S T R E E T
A P A R T M E N T  - 7 B
NEW YORK, NEW YORK
87996
Also, it would require replacing every return with a forced line break (attainable, but still.)
Solution 2: Use Nesting Styles
This *might* work, but I can't tell it to stop the nesting style with a line break/return, only with specific characters (which I would have to insert line by line and negate the whole point.
Solution 3: Use GREP
This is a foreign language from another planet and I CANNOT figure it out. I can set character styles no problem, but telling ID in GREP when to apply them is a mystery to me. HELP!
BobLevine EugeneTyson @P_Spier << you guys are my heroes!  InDesign

Answer 1

I don't think that's what he means. The Yahoo push mail uses Yahoo's IMAP which only works if you set up your account on iPhone using the preset Yahoo account setup. This setup does not allow for changing the FROM address, so the email appears to be from the underlying yahoo.com account. If you pay for Yahoo Plus you can use POP and change the FROM address, but then you don't get the benefit of the push email.
I'd love to hear a solution, but after calling Apple and Yahoo and combing the support boards of both, I don't think its possible at this time.