First off, using / in folder names isn't a good idea, since this is a directory delimiter in UNIX and may cause other problems.
That said, working this kind of logic into Automator is, mostly easy, the issue is parsing the folder names to find the last-used digit (Automator doesn't do this well, IMHO.
You can use a series of Automator Actions to:
Get Specified Finder Items (get your base directory)
Set Value of Variable (store this value in a variable for re-use)
Get Folder Contents (find all the items in it)
Filter Finder Items (filter out the directories)
Sort Finder Items (sort them)
and now you'll have a list of the subfolders. The tricky part (in Automator) is then iterating through those, extracting part of the file name to find the last-used number.
So that's where I'd just use a Run AppleScript Action with something like:
on run {input, parameters}
tell application "Finder"
set n to name of last item of input
set {od, my text item delimiters} to {my text item delimiters, "/"}
set thelastDigit to last text item of n
set my text item delimiters to od
return thelastDigit + 1
end tell
end run
This script takes the last item in the list (which was sorted by name), extracts the last element (note the above caveat of using '/' in file names) and returns the next-highest number
You should then:
Set Value of Variable (store this number in a variable for re-use)
New Folder (create a new folder using the variables you created in earlier steps to define the folder name ( e.g. "PathTo-<Today's Date>-<NewFolderNumber>" and the location where to create it (from step 2).
(note that in the above, the bold text indicates the name of the actions to apply)
Hope that helps.