Calculate 5 nearest point distances.

Hello,

I have two excel files with coordinate information, one (file A) is using lat/lon, the other (file B) is using Cartesian system (meter) under WGS 84 system.

File A has 20 points (house locations). File B has 200,000 data points (locations of events occurred).
My purpose is to calculate the distances of 5 nearest houses for each event.

Question 1.
How to convert the lat/lon in file A to the same unit as file B? Using "Define projection" as WGS 84?

Question 2.
Two situations:
A. If I can convert both the file A and the file B to shpefiles. How to calculate the distances of 5 nearest houses for each event?
I know "point distance" function can do all of them but I only need 5 nearest houses.


B. If I need to keep the file B as excel format, how to calculate the distances of 5 nearest houses for each event?

Thanks!