input mask

each element is a mark: an input mask is a character-by-character template, so each symbol in it independently controls one position of the typed value, which is exactly why a five-character mask like >LLL\-0000 is worth five marks rather than one. L not ? because L makes a letter compulsory — a required mask character blocks the record from being saved if that position is left blank, where an optional one (?) would silently allow it. 0 not 9 or # because those make digits optional, so "exactly four" would fail: with an optional digit character, a user could type only two or three digits and the save would still succeed, defeating the "exactly four" requirement. The dash is escaped with a backslash because Annexure A shows - is a separator that depends on regional settings, and \ forces the true character — without escaping it, Access might substitute whatever the system's actual separator character is, which isn't guaranteed to be a plain dash on every machine. Using > enforces uppercase by converting every character typed after it, rather than merely validating that uppercase was used.