Highlighting duplicate cells based on values in the new entry being made

Hi all,
I have a unique question.

How do I automatically highlight duplicate values ( number or text) in sheet data based on the new entry made.
e.g. I have sheet1 where I have column A to P.
A contains date
B contains location
C contains specific text
D contains Specific text / number and so on....

When some one makes a fresh entry and populates cells in column C & D then based on values of C & D , any duplicates in that sheet is highlighted in say yellow colour.

When the entry in column E, & F is made, ignoring the highlights, then all the highlights are cleared.

Do you think it is possible?
I have attached the sample book.

Regards

Hi all,
Any help yet on this one please?
Regards