Drop Down Properties

On my form which is designated

"Private Client Work Order - Document Upload - Payment"   The other Work Order template is also similar. 

I have built a drop down designated "Service Type Handling"  (2) of the option's within the drop down I have marked *Special and *Rush    below the drop down in the sub label I show *requires additional fee.

So, is there an ability to use the drop down and also using the calculation widget I have to be able to add specific charges to those two * option item's and have it automatically calculate if either one is selected and then have it show in the Subtotal.   I'd like to have this ability of possible rather than having to tell my client's to add this additional service amount manually into the quoted amount field to be calculated then into the Subtotal then to the Total Fee Due for the Payment?.    Unless there is something else I should use to achieve this type of option selection calculation method.

Thanks for the help on this 

You can make use of calculation values whereby there are monetary values attached to each option selected from the dropdown. You can then add those values to the calculation widget. 

Refer to this guide: How to Assign Calculation Values