Increment during insert

I'm inserting rows into a table based on the values in several other tables (joined).

I need to increment a "box number" during the insert, starting at 1 and incrementing each time a value in the box ID column (BXBID#) changes. There are multiple rows with the same Box ID in table RFPCKRBB.

Exec Sql
Insert into OEBOXCBX (bxridc, bxcom#, bxord#, bxrel#, BXBID#, bxbox#)
Select 'BX', bbcom#, bbord#, bbrel#, bbbid#, BOX_NUMBER_HERE
From RFPCKRBB
Where bbcom#=:inCom and bbord#=:inOrd and bbrel#=:rls and bbqty#>0
Order by BBBID#;

I'm almost to the point of reverting to SETLL and READE to accomplish this.

Thanks,
Greg