If you want someone to build this for you, by all means post in the Gigs & Collaborations part of the forum.
Otherwise, do a search on this forum as this kind of projects come by on a rather regular basis. Lots of info is out there and which works for you depends on many parameters that you didn't give such as speed and size required.
Other than that, for sure it's possible.
Detect the boxes using maybe a break beam sensor or ultrasound as they pass; use an RTC to have actual time; store counts on on an SD card or send it directly to a connected computer; export CSV file that you can directly import in a spreadsheet application such as Excel.