Dialog not working.

In the 'Trigger on new record' I have the following

let title := "Serial and/or Bundle Required";
let message := "Does this new record need it's Serial Number logged? 
If so is it part of a Kit/Bundle?";
let answerOptions := ["Yes", "Both", "Ignore"];
if dialog(title, message, answerOptions) = "Yes" then
    SERIALIZE = true;
    if dialog(title, message, answerOptions) = "Both" then
        SERIALIZE = true;
        'IS BUNDLE' = true;
        if dialog(title, message, answerOptions) = "Ignore" then
            SERIALIZE = false;
            'IS BUNDLE' = false
        end
    end
end;

The dialog does not function at all on a new record.  Why would this be?  Can someone assist please.

Cheers