Are you getting any errors?
If so, what are they?
Is there a default checked box for this radio button?
I would assign values to the export value of the radio button and make the 'No" button checked by default. You then set the export value of the "Off" radio button to 1 and the export value for the "Yes" button to 0.10. You can then do not need to use the custom calculation script, you could use the simplified field notation calculation option.
For the finalbasic value:
basic - (basic * angus)