AppleScript to Select Groups of 3 Files?

Question

Hi all,
Thanks in advance for any help you can provide. I am trying to create an AppleScript to take groups of 3 files and put them each in their own folder, inside of a master container folder. The files will typically be in DNG format as they will be from my digital camera—3 exposures of the same scene.
Input example: folder containing files IMG_0022.dng, IMG_0023.dng, IMG_0024.dng, IMG_0025.dng, ... IMG_0052.jpg
Output example:
Container folder hdr_images
folder images_group1
IMG_0022.dng
IMG_0023.dng
IMG_0024.dng
folder images_group2
IMG_0025.dng
IMG_0026.dng
IMG_0027.dng
folder images_group10
IMG_0049.dng
IMG_0050.dng
IMG_0051.dng
This is the script I have thus far, but I know there are errors and I can't get it to work the way I want:
-- begin script
tell application "Finder"
          -- Select all files in the folder selected from dialog box
                      set theFiles to files of folder (choose folder)
          -- Prepare to select groups of 3 files (1-3, 4-6, 7-9, etc.)
          set theInterval to 3
          -- Initialize the number of the group of 3 images
                      set groupNumber to 0
          -- Display dialog requesting location to create new folder
          set p to path to desktop
          -- Create new container folder in specified location
                      make new folder at p with properties {name:"seq_groups"}
          -- Loop through groups of 3 files, each time creating a container folder
          -- and copying the 3 files to that container folder
                      repeat with i from 1 to (count theFiles) by theInterval
                                        set groupNumber to groupNumber + 1
                                        set itemsToCopy to null
                                        set itemsToCopy to item i of theFiles
                                        set itemsToCopy to itemsToCopy & item i+1 of theFiles
                                        set itemsToCopy to itemsToCopy & item i+2 of theFiles
                                        copy files itemsToCopy to folder ____
          end repeat
          -- Display message box confirming success
end tell
You can see from the comments that I'd like to have it flow as follows:
User either drags a folder onto the script, selects from the Services menu, or runs the applet to get a dialog box to choose folder
Applet runs on all images within the folder and copies, rather than moves (just in case something goes terribly wrong)
Applet confirms it is finished
Any help would be greatly appreciated. Thanks again!

Answer 1

Thanks, I played with it a bit more and this is the final result after more googling:
tell application "Finder"
          set source_folder to (choose folder with prompt "Choose Source Folder")
          set container_folder to (choose folder with prompt "Choose Destination Folder")
          set the_count to 1
  sort files in folder source_folder by name
          repeat ((count files in folder source_folder)) div 3 times
  make folder at folder container_folder with properties {name:"images_group" & the_count}
                    set the dest_folder to folder ("images_group" & the_count) of container_folder as alias
  duplicate files ((the_count * 3) - 2) thru (the_count * 3) of folder source_folder to folder dest_folder
                    set the_count to the_count + 1
          end repeat
end tell
The only problem I continue to have is that it's not going by the "Finder order" of image sequence. Because each group of 3 is a different "scene" I need to make sure that wherever the file numbering sequence starts, it goes in order. Ideally, I'd like for it to read the metadata from the image files (they're all in DNG) and sort by capture time, but that seems a bit outside the scope of AppleScript's capabilities. Thank you again for your help!