Comparing points in 3D

Hi there,

Quick question (hopefully!), I've got a large selection of data (~39,000 lines) each of which has X,Y,Z and an identifier, if I want to compare this identifier to the surrounding points in 3D space, currently I've got a for/if statement combination, but its taking an absolute age. Considering the Volume of these I want to run, its just not practical. I'll give an example below;

• 508000 2023000 -10000 3
• 508000 2023000 -9500 2
• 508000 2023000 -9000 3
• 508000 2023000 -8500 3
• 508000 2023000 -8000 3
• 508000 2023000 -7500 3
• 508000 2023000 -7000 3
• 508000 2023000 -6500 3
• 508000 2023000 -6000 3
• 508000 2023000 -5500 3
• 508000 2023000 -5000 3
• 508000 2023000 -4500 3
• 508000 2023000 -4000 3
• 508000 2023000 -3500 3
• 508000 2023000 -3000 3
• 508000 2023000 -2500 3
• 508000 2023000 -2000 3
• 508000 2023000 -1500 3
• 508000 2023000 -1000 3
• 508000 2023000 -500 3
• 508000 2023000 0 3
• 508000 2023000 500 0
• 508000 2023000 1000 0

Basically I want it to return the information about if the identifier (lithology in this case) is different to the surrounding nodes in 3D space.