I have a spreadsheet listing out employees, e.g. as follows:

Name Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Total YTD%
A N Other 1 0 0 0.5 5 0 0 0 0 0 0
0 6.5
F Smith 0 0 0 0 0 0 0 0 0 0
0 0 0
M Brown 0 0 3 0 0 0 0 0 0 0 0
0 3

Days of Mth 20 20 22 19 21 20 20 21 22 21 22 21
249

I need to as an example total the days of month up to end of May (being 102
days) and subsequently in June (122 days) etc., to calculate the YTD % per
person.

Many thanks in advance for any help provided.