Add Items in the combo box on the fly

Question

Hello Team, 

I have a form which has a combo box named as state. I have a scenario where if the user wants to add a state which is not present in the combo box on city form, i have given a button which opens another state form without closing the city form, where the user can enter new state. Once the user enters the state, he will close the state form and come back to city form and here the new state should be made available for the user to select, without refreshing the form, neither clicking a button. 

Note : I have binded the combo box on form load with dataset as its datasource. 

Basically i want combox box to be updated automatically whenever there is new data been inserted into table, without refreshing or firing any event 

Regard's 
Raj.Trivedi 
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