A long time ago, back before our error trapping was robust (see this document for more information), agents would error out with numbers that didn't have any meaning. What's the error number 9 mean, anyway? So we wrote a quick agent to check out the error number and give us a value (9 means "Subscript out of range").

Sub Initialize
   Dim num As String
   num = Inputbox("Enter the error number you would like to check", "Enter Error Number", "")
   On Error Goto TrapError
   Error Val(num)
EndOfAgent:
   On Error Goto 0
   Err = 0
   Exit Sub
TrapError:
   Msgbox "Error " & num & " = " & Error$
   Resume EndOfAgent
End Sub

The code first prompts for the error number. When testing this out, try "11", "13" (a favorite one), "28", and some of your favorites. The code then, on purpose, creates an error of that error number. But the error is trapped. So we can print out (through a message box) the Error$ value, which is the text version of the error. The code then resumes, which clears out the error handler and exits.