count how many tims a certain value occurs

[lucnijs]

Hi!

I have a spreadsheet for the amount of times students practised their instrument and for the help they get from their parents

so I have 2 columns per day, one for the amount of time practised and one to indicate if and by whom they were helped.
e.g.
F = Monday_practiceTime
G = Monday_helpedBy


H = Tuesday-practiceTime
I = Tuesday_helpedBy
J = Wednesday_practiceTime
K = Wednesday_helpedBy
...

I now want to see how many days they practised a week.
See I was thinking to count the cells with a number greater than 0.
I used COUNTIF:

COUNTIF(F2+H2+J2+L2+N2+P2+R2, ">0")

But I get an error message saying that the range is invalid.

How can I do this right?
I use Excel for mac 2008

Thank you!

Luc