Combining If and Lookup for Complicated Data (Sample is attached)

Hi

I have to match year-ended of each firm with market value (MV). In my criteria, I am looking for value of MV 4 months after the firm's year-ended.

For example: If firm A has its year-ened 30/06/07, I am looking for MV at the date 31/10/07 (another issue is sometimes the date for MV can be 29/10/07, not 31/10/07; however it can be varied +- 7 days of the firm's year-ended date).

Please can you help me how to match these data. I also attach the sample of my data.

Thank you very much.