Updating total when using gform_product_total and other fields

Hello,

Background Info:
This is an order form for a text ad listing. There is a commercial rate and non-profit rate. The user can select how many months they wish for their ad to run for. Using product field and quantity field works perfectly to update the total. My issue is in a second option to allow the user to 'upgrade' their listing with an image (checkbox field) should add $25/month to the total.

Here is my setup:

Product:
Commercial - $50
Non-Profit - $35

Options:
1 Month|1
2 Months|2
...
12 Months|12

Upgrade?:
Checkbox (default is unchecked)

My function to update the total:

function gform_product_total(formId, total){
        if (jQuery("#choice_22_1").is(":checked")) { //Checks to see if 'upgrade' checkbox is checked or not
        	var monthRun = (jQuery("#input_12_20").val()); //Product options drop down with options for 1-12 months with values of 1-12
	        var logoCost = (25 * monthRun); //Computes additional cost if checkbox to use logo/image is checked
    	    return total + logoCost; //Computes total of additional cost and base cost of product
    	} else {
    		return total;
    	}
    }

This function updates the total properly but it won't auto-update the field. I have to go back and click on the radio button for the product type, e.g., commercial before it updates the total.

How can I force the total to update when the user checks the upgrade box?

Also if you have any recommendations to make my function cleaner I'm all ears.

Thanks

Continued messing around with this today and solved my issue (although somebody else might have this issue in the future).

When somebody clicks the 'upgrade' option I set a File Upload field to display using conditional logic below the checkbox which fires the function to update the total.

While this solves my problem somebody else might want this functionality but not need an additional form element displayed when a box is checked. Maybe an alternative way to update the box would be to create a blank hidden field that displays when a box is checked? I'm not for sure if that will update the total but it might. I did not try this but just thought of it in case somebody stumbles across this.