I'm sorry about the delay in response to this. With our transition to the new platform, this question was originally answered on the previous site but the response did not get copied over to here. I am re-responding now for your reference.
Unfortunately Orthotrac does not record information about posted, printed or confirmed letters (other than the document that is written to document storage when a letter is confirmed for a specific patient) and so there are no reports that will provide this information at present. If you can, please let me know what this letter is being posted for and perhaps I can give you some other way to obtain this information (for example, did all of these patients have a specific procedure posted? Were all of them seen in the office during a certain date range? Etc.)