I think it is realy time for you to grab SQL Reference manual and learn a few basic things about character functions. I've given you a sollution for very simmilar question (on a diferent thread you started under the same title as this sone), however it seems that you don't learn very much from the answers to your questions. If you think others will solve any trivial task you stuck with, you won't get very far in this...
Anyway, the answer to your question is:
SUBSTR('abc123',1,2) || '#' || SUBSTR('abc123',4)
Jurij Modic ASCII a stupid question, get a stupid ANSI
24 hours in a day .... 24 beer in a case .... coincidence?