Hi Anne-Marie,
All of the above advice is right on the nose. Here is the way I look at it:
Go through all the steps to prescribe the controlled medication, through Amazing Charts, as if it were a non controlled prescription. Pick the medicine, quantity, refills if appropriate, and so forth. Then when you actually come to the transmit page, if the pharmacy is listed, just exit and go to New Crop.
If the pharmacy is not listed, then select from the Amazing Charts screen, as you would a non controlled medication. Hit transmit, which of course will fail. Then go to New Crop.
It sounds very cumbersome, but with experience it's really not so bad.
Hope this helps!
Gene