conditional formatting

Hi Guys

Cells B10:B107 contain the formula

=IF(O10="","",NETWORKDAYS(TODAY(),O10)&" days ")

which acts as (in this case) a deadline countdown which tell the user how many days there are left to respond to a complaint.

I wanted to add conditional formatting so it is very clear at a glance which ones are urgent.

Red = <=5
Amber = Between 6 & 9
Green = >=10

The issue i am encountering is the the Blank Cells within the range b10:b107 (blank as Col 0 is unpopulated) are appearing as (Format) green I would like them to be left without formating! Any ideas on how to achieve this ? cheers

See database tab of attachment col B

Thanks for your response.