Hi MickyT,
Thanks for your help.
This is what I needed, and I got there with your reply.
CASE WHEN substring(xlCode, 16, 1) LIKE '[0-9]' THEN substring(xlCode, 15, 1) ELSE substring
(xlCode, 15, 2) END AS GroupNo
, CASE WHEN substring(xlCode, 16, 1) LIKE '[0-9]' THEN substring(xlCode, 16, 4) ELSE substring
(xlCode, 17, 3) END AS SeqNo