Highlight text field

[eugz]

I have the Inventory Form. So the some fields cannot be empty and cannot duplicated. I asked user to enter temporary data like "?NNN" where NNN is sequence number. But if I will have a lot of UNKNOW value to maintain DB became dificult. Is it posible to highlight backcolor and font fields with value like "?NNN"? If YES how it to do?
Thanks.

 

[eugz]

Thanks Pat.
What about color? Is it posible to highlight background of field?