On Change Event does not trigger on the column/field if the column gets set the value by another script

I have the web resources ( HTML + Script 1)  which used for search Addresses in Australia and the retrieved value/chosen value will be autocomplete and set to the fields as below. This web resources was developed by the previous vendor.

Now I build another webresource (Script 2)  and build a function called OnChange_Address1 State/Province which gets trigger on change of the Address 1 State/ Province. It perfectly trigger/fire if I manually go and update the Address 1 State/Province

But If the user search for the address and Script 1 populate the changed value to Address 1: State/Province, The Script 2's function OnChange_Address1 State/Province does not get trigger.

I was able to solve this issue by modifying the Script 1 and add the fireOnChange Method to the attribute. which I do not want to modify anything in Script 1 as it developed by previous Vendor. 

Kindly, If there is any solution to trigger Address1: State /Province column when user search get populate to the field without modifying the Script 1 and add some code in Script 2 ?