sql insert into and increment id

Have a normal file keyed by one column.

It is not an option to change this column to auto increment...



I can add single records with insert statement where the key field is
"max(field) + 1" -



In the values

(select keyfld = max(keyfld) + 1), itemName,itemType.



But if I do an insert that has selected multiple records - I get an error
the keyfld not unique



Insert into itemMast

(keyfld, itemName, itemType, qtyOH, Location)

Select (select keyfld = max(keyfld) +1), itemName, 'A', 0, Location

From itemMast

Where itemType = 'B'



Is there a way to do this without altering the definition of the file
(package software)?

We need to duplicate a large number of records, but with unique keys.



Jim