Thanks again for the advice. I'm thinking this might be a limitation of 3.0 and/or 3.1 because I get a different result to TribbleSmasher with a similar script.
The top box is my text script. I'm echoing the variables to debug them and the second window is the output demonstrating that I'm setting the values correctly.
The third window is the RequestChoice box showing the first value displaying correctly but the second isn't, being replaced by the command.
I've tried a few different combinations including $ variables, SETENV and GETENV, backticks and {} but still don't get the desired output in the RequestChoice box.