How do you write an If/Then statement to mark a check box if getField is true

How do you write an If/Then statement to mark a check box if getField is true?

I have a YES and a NO check box next to if they have a "widget". The excel spread sheet has an "X" if they do have a "widget" and it is blank if they don't.

I want the YES box checked if there is an X or the NO box checked if it is blank.

Thank you,

Bill