If Statements and blank cells

Hi everyone,

I'm trying to solve a problem I have with an IF statement and blank cells. I've got a worksheet called "Product Register" which contains details of products (serial numbers (col A), description (col B) and expiry date (col C)). I'd like to add four columns at the end of this sheet as follows: Expiry date unknown, Expired, Expires in 30 days, Expires in 90 days. I've put the NOW() function in cell D1 to give me todays date. Some of the expiry dates of products are currently unknown so Column C may contains blanks. Can anyone give me the function to write into each of the following please returning a "Yes" in only one of the columns:

Expiry date unknown:
Expired:
Expires in next 30 days or less:
Expires between 30 days and 90 days:

Any help much appreciated

N

Thanks so much etaf!! You'r approach is so much simpler, I was tangling myself in knots trying to have the categories in separate columns. So simple when you look at it! D'oh.

Thanks very much for your help