Zend certified PHP/Magento developer

Add cells then subtract 1 if there is a date in another cell

So I am creating a spreadsheet that I track peoples Comp Time. What I am wanting to do is in, say F3 has a beginning balance of 2. Through out the month the gain some additional days (G3=1, H3=2, I3=1, J3=0). in K3 I want to be able to put a date/dates that they used some of the comp time and in L3 to equal the sum of F3 thru J3, then subtract 1 for date that is in K3.

To summarize – F3 (Beginning Balance) has 2, G3=1,H3=2,I3=1,J3=0, K3 (Date(s) Used) has 2 dates of May 5th and May 8th and then L3 (Ending Balance) should then equal 4
F3:J3=6, then subtract 2 because K3 has 2 dates and L3 sum it all up and come up with a total of 4