Excel 2000 - show billable days

I have been asked to create a spreadsheet that will contain three fields;

Date of placement (the day the person arrived)
Date of release (the above + 60 days)
Billable days for the current month

The first is simple, the clerk will enter the current date when the person arrives.

For the second field I am using:: =SUM(H5+(60),) (H5 is todays date, and will display the results in I5). When H5 is blank, I get the " #VALUE!" error in I5? Is there a more effective function to use?

For billable days, I am using; =SUM(J2 - (H5),) (J2 is simply the last date of the month; 12/31/09, and H5 is the placement date). I want to show the number of billable days in the current month. This will be repeated on 12 sheets (one for each month).

Any suggestions greatly appreciated,

Thanks!
Ralph