You could use the DATEDIF function to give you the difference between
two dates in years, months or days - take a look here on how to use
it:

http://www.cpearson.com/excel/datedif.aspx

A simple approach, to give you the difference in days, would be:

=IF(B1="",TODAY()-A1,B1-A1)

Format the cell as General or Number.

Hope this helps.

Pete

On Dec 22, 12:36*pm, Kim wrote:
Can anyone help please? *I want to calculate employee length of service from
start date (A1) where there is a leave date (B1) or (B1) is blank and should
use TODAY as the reference date.