I generally opt for using a helper cell in these situations and use Data validation with the Custom Option to check the helper cell.

Helper cell contains a formula; =A1="Early Shift"
It returns either True or False

In column-D cells using data validation, custom option and this formula:
=G1=TRUE (adjust cell reference, obviously)

If G1 = False, data validation with errror alert set to Stop will prevent data entry. Customize the alert message as required.

You could also use the above formula in a Conditional Format to change the cell color to highlight the cell when entries are required or not.