Finding 2 points on either side of 0

[saivior]

I have lists of data that go from -45 to 0 and back to -45, with a column of corresponding values. I need to find the two points closest to -2 and find the difference between their corresponding values. Also, I need to find the average of the previous function.

I tried V-lookup, but that was only able to find the first of the two points.

I have attached a workbook with my current formula, in which I need to manually find these values.

Any thoughts or ideas would be greatly appreciated.