Could I perform PWM through this?

The circuit diagram on this page (sorry for my scruffy diagram) is from a radio controller.
Although I didn't know it at the time, the big question mark which several points in the circuit connect to, is actually an encoder chip (allowing multiple messages to be sent on the same frequency).
I was just wondering whether if theoretically I could attach this to an arduino board and use the pulse width modulation feature from there instead?

Thank you for reading

You have four buttons that earth various pins on the blob. You seem to have left the crystal circuit disconnected from the blob. I suspect that the blob contains an oscillator whose frequency is determined by the 200K resistor. sort of like a HT12e but with extra gates and the RF side. So the simple answer is no you can not. If you are really pushed you could set up a combination of switches and try to feed your arduino input into the 200K pin, but you would have to find experimentally what it actually does.
Frank