Petitioner Start Date & End Date for H4 Visa? based on H1B two i797. very urgent

[chatra]

I have current i797 valid until march 2013 and have a approved i797 from 2013 april to 2016 march.

Need to fill H4 for my wife.

What would be the petitioner start date for H4 and End date request ?and also which i797 Receipt number I need to fill with while applying H4 ;current or future receipt number of i797 if she has to come with me this december 2012?

Thanks in advance

[sai shivam]

i am in the same boat. can somebody please reply soon.

Thanks in advance.