Illustrator Scripting :: Using Javascript And ScriptUI To Create A Form That Brings In Symbol From Library

I've been trying to pull together the right info to use JavaScript to create a form to bring in particular symbols from the symbol library based on the variables taken from the form. I've taken bits and pieces from various sample scripts and tried to make this work, but my problem appears when I try to use conditionals.This is a limited version of what I want to do, but it is enough to get the point across.
 
1. I want to select a script that has various dropdown boxes. I would like the first dropdown to give me 3 options: 10, 13, 18
2. I would also like another drop down box that gives me three more options: single needle, double needle, and knife edge.
3. I would then like it to have an "ok" button and "Cancel" button.
4. From here when I click the ok button, a symbol is brought in from the library depending on what parameters were given to the form.
 
ex. If I selected 10 in the first drop down and double needle in the second, I would like "SYMBOL A" to be pulled from the library and centered on the artboard.ex. If I selected 13 in the first drop down and double needle in the second, I would like "SYMBOL B" to be pulled from the library and centered on the artboard.
 
I've gotten the UI to pop up and it works as planned as well as bringing in a symbol, my problem comes when I try to incorporate conditionals and functions.Here is my script.
 
var myDoc = app.activeDocument;var Pallette = new Window ("dialog", "Create a Shell"); Pallette.add ("statictext", undefined, "Fill Opening in Inches:"); Pallette.orientation = "row";var myDropdown =  Pallette.add ("dropdownlist", undefined, ["10", "13", "18"]);myDropdown.selection = 1;var myButtonGroup =  Pallette.add ("group");myButtonGroup.orientation = "column";var btnCreate = myButtonGroup.add ("button", undefined,
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