Better to split the I'd column into two to separate the numerical prefix. This could then become an identity if you wish - but you probably don't want gaps to support the letter equivalent so populate it using a trigger. Now you can generate the letter when the table is accessed using a computed column or view. You could use the trigger to populate the letter as well as the numerical value if you wish. Do you not want to allow for more than 26 rows?
========================================== Cursors are useful if you don't know sql. SSIS can be used in a similar way. Beer is not cold and it isn't fizzy.