Excel 97 question

I have a date field on a spreadsheet that accepts the entry of zero, and that places a literal string in the cell, (I have it displaying the string “need date”). If you look at the formula bar, the custom date code says 1/0/1900.

It also acceptsa regular entry of a date if I choose to enter one.

My question is:

I want to put a conditional format using code in these cells as well. I want the formatting to read something like…

If date <= today(), BOLD & ITALIC, if not NOTHING. Since the value in the cell is a display value only, will I be able to do this?