Radio Button to make other field Mandatory

I have two Radio Buttons that I want when clicked on (either one) to make a Number Field mandatory. I have viewed many websites on setting a mandatory field but the script I am using will not work. I have tried a couple ways of writing it but I seem to be missing something.

I have used this script in the Show of: click & change

Here is the script that I'm using right now.

AssemblyNu-1.mandatory ="disabled";

And this one:

if (this.rawValue==2)

Thanks,

HHud5757