Eliminate intermediate columns

I have a spreadsheet with a column B containing data like this:
Dark-Shadows-0247.avi
Dark-Shadows-0248.mp4
Dark-Shadows-0249.mp4
Dark-Shadows-0250.mp4
Dark-Shadows-0251.avi
Dark-Shadows-0252.avi
Dark-Shadows-0253.avi
Dark-Shadows-0254.avi
Dark-Shadows-0255.avi
Dark-Shadows-0256.avi
Dark-Shadows-0257.avi
Dark-Shadows-0258.avi
Dark-Shadows-0259.avi
Dark-Shadows-0260k.avi
Dark-Shadows-0261.avi
Dark-Shadows-0262.avi
Dark-Shadows-0263.mp4
Dark-Shadows-0264.avi


I want a count of mp4 files and avi files. So I created a column AA with a formula like =RIGHT(B2,3) which gives me a column containing just "avi" or "mp4". Then at the bottom I can use: =COUNTIF(AA2:AA1226,"mp4") to get the count of mp4 files. There is other stuff encoded in my filenames. That 260k.avi is a kinescope. And column AB has formulas like: =LEFT(RIGHT(B2,5),2) which in the case of a kinescope results in "k." in the column. And then at the bottom, =COUNTIF(AB2:AB1226,"k.") gives me a count of kinescopes. This all works great. I don't even need to hide columns AA, AB, ... since they are so far over. Still, just for the elegance of it, I would like to eliminate these extra columns and use count formulas that work directly on column B. I have tried a number of formulas but none of them work. Is there some easy way to this this?

I am using Microsoft Office Home and Student 2010 and Excel is version 14.0.7163.5000 (32-bit).

Finally, note that I have a working solution for everything I need and a heroic substitute like resorting to Visual Basic would not very attractive. At some point, elegance loses out to ease of maintenance. Thanks for any help you can suggest.

Thanks for the fast responses! And =COUNTIF(B3:B1226,"*k.*") is catching the kinescopes.