New H4 Visa Petition Number with Visa expiring a month after entry to USA

[letsplaysudoku]

Hi,
I had the following question regarding my fiancee's H4B Visa.

- We are getting married on July 31, 2015
- Planning to go for H4B Visa Interview on 1st week of Aug
- My current H1B Visa expires on Sep 30, 2015 and I would be applying for a Visa extension next week. ETA for extended I-797 & Petition to be available is 1-3 months.
- If I use current Petition number for the H4 Visa DS-160, she would be getting a Visa Stamp only upto Sep 30, 2015. If she uses the new petition # once it arrives, she can enter US only on Oct 1, 2015 (new Visa date for H1B)

Can I use current petition # in H4 DS-160 and later for the interview she carry new petition number (for my new I-797 extension which will be valid from Oct-2015 to Sep 2018) and expect her to be stamped till Sep 2018 ?

If not, what are my choices ? Please let me know if you have any quesitons.

Thanks for your help,

[fasy]

h4 visa

With just one month validy left,if u apply for H4 for your spouse in August,will you get the H4 visa approved??If u apply with old visa number?