Automatically having text added to one cell

Hello,
I am looking for conditional formatting only. I want to have text entered in one cell based on text in another cell.
Example: If cell "A" is blank and cell "B" has the words "Male" or "Female" added to it (from being blank previously), how can I make cell "A" display the word "DUE"?
If that is not possible, if cell "B" has a date entered in it (from being blank previously), how can I make cell "A" display the word "DUE"?
Thanks in advance,

Chris