I havent done this on a 31i control, but the following works on an 18i-TB and some earlier ones too like a 16i and the LE series
-On the computer open up the program you want to send.
-Change the program number to anything besides a 9000. (I usually do 00## with the number I want to change it to, so 9012 would be 0012)
-Load the program into the machine as usual as prog # 0012.
-Go to edit and select the program # with the cursor.
-type in the 9000 number you want it to be and hit Alter.
Let me know if it works!