c # – Show updated price of a set price list after changing options in the list box

Creation of a program in the visual study for a meal order service where the user obtains a list of meals and a list of meal sizes. There is a fixed price for each meal with each size, eg. Full child in English = 3.40, full adult English = 5.00. I need the price of the order label to be updated instantly when the selections are changed in the list box. If any of the selections in the list box change, the price should be updated. Accumulated totals will not work since the price list is already available.

Below is a screenshot of my form.

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I am using the switch box with the list box and then the radio buttons embedded in each change instruction