Hi,
The NI-USRP driver ships with a few Modulation Examples which use the Modulation toolkit to transmit and receive wave-forms with different modulation schemes using USRP devices. You may be able to use them as a starting point to create your OOK application.
I didn't however the myRIO part in your post. Can you elaborate?
"I will run this files under the USRP NI myRIO"