Checkbox Formula: If Due Date has passed but completion date is blank

I have two columns:

1: A "Date Calc" field (contains a formula) that automatically displays a due date for a task based on manually entered dates from a prior field. This is a date column.

2: A Date Complete field that is manually entered. This is a date column.

I have added a third column that will automatically check a box if the Date Calc field is:

1. In the past
2. The Date Complete is blank

I do not want the box to be checked if the Date Complete field is NOT blank.

I have used the following formula which is almost there, but it is triggering a checkbox for dates in the Date Calc field that are NOT in the past.

This is what I am using: =IF([Date Calc]@row < TODAY(), ISBLANK([Date Complete]@row), 1)