The OnObject Modify trigger can be set on the field to perform a single script, But the script can check the value of the radio button field to determine whether to do the steps for option 1 or option 2:
IF [ table::radioButtonField = "FirstRadioButtonValue" ]
Put steps you want for first radio button value here
Else If [table::radiobuttonField = "SecondRadiobuttonValue" ]
Put setps for second radio button value here.
This script assumes that the user did not hold down the shift key and select a second value.