Say you want your button click to select "Apple" in a radio button field that lists two values; Apple, Orange:
Set Field [YourTable::YourRadioButtonField ; "Apple"]
to set the date in a field:
Set Field [YourTable::DateField ; Get ( currentDate ) ]
If you want the same button click to do both, use perform script to perform a script that includes these two steps.
Note: When Setting up Set Field, there are two Specify buttons that must be clicked. To get Set Field [Table::Field ; Expression], add set field to your script and click the first button (specify target field). Select Table::Field from the list of fields. Do not click the specify button next to the repetition box. Click OK to close this dialog box. Now click the lower specify button (calculated result) and create the expression to the right of the semicolon (;). Do not try to type in the semicolon.