This is something that we used to set up for people that wanted the system to either add a leading 1 to long distance calls, or delete the 1 from local calls, usually in areas where a single area code spanned several latas.
You can use either FCAS tables if you know the specific exchanges within each area code that would require a 1, or you could just build a DMI that would add the 1 to all numbers that hit a particular RLI.
For instance, if your callers dial 9301NXXxxxx (ACOD+NPA+NXX+xxxx) and LD 90 is set to send that call to RLI 1, then just build a DMI in LD 86 that inserts '1', and enter it in the DMI prompt for your entry's in RLI 1.