Digital signature dictating where data is input

Question

The form I have is a government form that has varouis areas to sign.
Here is the sceanrio:
Evaluation type A
Evaluation type B
I have a main menu that is centralized that populates data for the entire form (alot of the data on these forms is repetative).
Both are check boxes; only one can be checked.
On my main page, it has a supervisor signature.
If the evaluation is type A, how do I direct the signature to populate in a specfic locked field?
Can i use the this.getField method to generate that digitial signature on a box and reproduce it in other pages?
I am assuming I have to use an If statement, for example:
If Box A is checked, Field X = Field Y

Answer 1

Let me modify my question as to make it more easier to understand.
I have 4 radio buttons under this scheme:
Group: MainCheckbox
Buttons: Choice 1, Choice 2, Choice 3, Choice 4
My questions are:
1) What is the syntax of an if statement in JavaScript if choice 1 is true? For example, this is what I am trying to code but it is not working:
if(MainCheckbox.choice1=="true") {
    event.value = this.getField("DateSignedEmployee").value;
2) If I digitally sign one block, I want that digitital signature to permiate to other selected fields. How do I code that in Javascript? For example:
if(signature15==signed) {
     signature16 = signed;
     signature17 = signed;
Obviously that is not the right code, but this is what I want it to do.