Macro or Custum Function to achieve +/- 10% of a value

Dear All,
I am using Excel 2010.
Please see the attached file for the problem.

I have made steps to indicate my problem and colored them for ease of understanding.

Step 1 – Check Values in Col F. If negative then eg F16 (which was negative and replaced)
Step 2 – Check the value in the corresponding Row in Col H eg H16
Step 3 – Look up and down for 4 values within +/- 10% of the value in Cell H16
Step 4 – Look up corresponding value against the values within 10% (do not include negative values)
Step 5 – Add all the values in Col F excluding the negative and divide it by 8 – Result is 1.843 in Cell F16

A macro or a Custom Function to achieve my requirement would be highly appreciated.
Thanks in advance.
Rashid

Hi
Thanks for your reply.
The value in F16 was also negative which was bigger than the value in F12.
We always go with the highest negative value.
The value shown in my sample data is already replaced manually (See the Formula bar)
Hope it is clear now

Any help on my problem please?
Regards