Solution found to mysterious variable not defined error in Google.
I was at wits end.  I modified the Holiday Card database slightly to add several Boolean fields to help indicate whether we sent a letter (in addition to the Xmas card) to a family, and if we received a letter.  My tables are called FamilyT instead of CustomerT, and CardHistoryT instead of ContactT.  I added Boolean fields SentLetter, GotLetter and NewUpdate to FamilyT.  I set the SentLetter field manually but I want to set the GotLetter field when I am updating the LastReceived field in my Card Mailing List (Customer List) form.
When I double-click the LastReceived field, it adds todays date to the LastReceived field, it sets field RecdThisYear to True, it sets a field called NewUpdate to True (Used as the criteria for the update and append queries for the FamilyT and CardHistoryT tables), and asks the question via a MsgBox("Did you receive a Christmas letter?", vbYesNo).  If the answer is yes, I have the statement GotLetter = True, then End If.
Further it refreshes and runs two queries, to update the LastRecieved field in the FamilyT and to append the date and message to the CardHistoryT using NewUpdate = True as the criteria.  Then sets NewUpdate to False, does a Requery, and exits.
The problem:  When I tried to execute the event, GotLetter got a compile error:  Variable not defined.
I checked the spelling, copied and pasted even changed the name to no avail.  Three other fields from CustomerT were parsed and updated without error.  If I commented out the statement GotLetter = True, everything worked correctly.  All fields in both tables were updated correctly and the date and message were appended to CardHistoryT.  I made certain GotLetter is a field in every query.
The solution came from a Google post that suggested I add me! in front of Gotletter.  I changed it to me!GotLetter = True and everything now works correctly.  However, I really dont understand why this was necessary for this one variable name.