Access - auto fill combo box based on multiple fields?

first off, thank you for taking the time to look at this.

I have a form that calculates sign up dates. if a date is present we consider the person "active". if the date isn't present we consider them "inactive" There is a total of 10 text boxes for the dates labeled "1 Diamond Date, 2 Diamond Date, 3 Diamond Date, etc".

I would basically like to write code to state that my combo box on top of these fields will auto populate "active" if one of the boxes is considered "not null" or go "inactive" if all boxes are "null". Any ideas?

Thanks Again!