Excel 2007 : Vlookup w/ variable limits and values?

I am having a problem with Excel and it's (...my) ability to find appropriate values for comparison. I have a large string of data (20000+) that varies both positive and negative. I want to pull the displacement value for the closest magnitude with opposite sign that is next in the data sequence; problem is that the data varies inconsistently.

I have tried vlookup with the true definition (as close is good for me), but with the variable limits of the loading it become a manual and tedious process to change the limits for the vlookup function as I only want it to consider the next closest number, not the rest of the entire set.

I have attached an example sheet with an example and a small set of the actual data for aid in understanding of my problem. What I would like to happen (looking at the example) is to find displacements for cells C2 to C9, using the string of data in rows 17 to 29. Basically, I want the displacement value for -A2, -A3....etc by looking at the data ahead of it. I have a vlookup written that works, but I have to change the array limits for each set (Row 2-9 used Row 9-17, etc) within the sequence. I am just trying to find an easier way.

If anyone has any advice, I would greatly appreciate it.