The older RCs used to automatically enter program mode when you tried to download... both good and horrible.
You can take a pwm cable, and cut the red and yellow (or white) wire. Reconnect one end of the red wire to one end of the yellow wire. Leave the other pair disconnected. Then stick the end with the connected yellow wire into a digital I/O, and the end with the connected red wire into the program header.
Diagram:
Code:
DIO PH
B -------------- B
R -- -- Y
Y -------------- R
In software, set the pin to high (1) in the initialization - don't forget to make it an output. When you want to enter program mode, set the pin to low.