Add mechanism to create a number/letter sequence and use the sequence inside a specification/document. Need to enable multiple parallel sequences. E.g. the PICS/PIXIT item numbers in a table - would require separate sequences for each set of numbers (e.g. 5.1.12, 5.1.13, 5.2, 5.2.1). Need to be able to start a sequence from 1, or continue a previous sequence.