How to make checkbox react to adjacent checkbox in Excel

I have 2 columns of checkboxes (from "Form Controls") in Excel (2010) that will indicate whether one of two tasks are completed. The 2nd task cannot be completed until the 1st one is done, but there could be instances where both tasks in a given row are completed in the same day. To avoid any extra clicks, I would like to make it so that if the 2nd task is completed (and checked) then the first task becomes automatically checked.

How do I do this?

For example:

I want to be able to manually check cell B5, but if cell C5 is checked, I want cell B5 to be automatically checked.

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I know I could "cell link" the second checkbox column to a 3rd column to create an output, but I don't know how to make the first column checkbox reactive to that...