Generating 'Key' via VBA Macro

Hello everyone,

I've a large data set, 17,000 rows, many columns etc.
I basically need to compare combinations of data between two columns. My idea was to create a 'key' column that basically combined the data together making it easier to compare and see where variations may be. The only problem, at least for my skill level, is that the data i needed to combine was split between multiple rows - not columns. I've been searching how to do this and read this can be done via an array formula; however, I know this can soak up a lot of resources on large data sets and I read that may not be the ideal solution - that a VBA solution may be best.

An example of the data I may have is below with an example of what I'm trying to achieve on the rightmost column. Teh result can be displayed in an adjacent column, worksheet, etc. - whatever is easiest.

Does anyone have any ideas/thoughts?

Column1 Column2 Desired Result
1.1.1 A 1.1.1,A,B,C
1.1.1 B 1.1.1,A,B,C
1.1.1 C 1.1.1,A,B,C
1.1.2 D 1.1.2,D,E,F,G
1.1.2 E 1.1.2,D,E,F,G
1.1.2 F 1.1.2,D,E,F,G
1.1.2 G 1.1.2,D,E,F,G
2.1.1 H 2.1.1,H,I
2.1.1 I 2.1.1,H,I

Thanks in advance!

Wow, you guys are fast! - Thanks so much!

Arkadi,
Your code worked beautifully on the sample I had! I modified the columns to match the main document and after freezing for awhile it actually did EXACTLY what I was hoping... Thanks SO much! Much appreciated.

Kev_,
Sorry about the clarity of my initial post. It looked nice when I was typing it in but got distorted when submitting. I'll make sure to post an excel file next time.
The letters in the same were part of column2
The values can vary in format unfortunately.

Kaper,
In reality I work in architecture and I'm dealing with an equipment list. Column 1 would be a number designated to a room and column2 an id code for the equipment belonging to that room. I'm basically trying to combine the number combinations with the equipment combinations to determine similar conditions to apply 'templates' to those rooms.

I just got Arkadi's code to work, I'll actually try out yours as well as I'm always excited to see multiple ways of doing the same thing!

Thanks again so much everyone for your help! It's greatly appreciated!