IF Formula for string of cells

Hi,

I am creating a timesheet for my team and have a problem. Currently staff members select an abbreviation of their name from a drop down on a sheet with all the days of the year on it, and that populates other sheets with other data.

I want to be able to note when staff take 10 consecutive days off, so want a formula to return a certain value if, in a whole sheet, there are ten consecutive cells within any set of 12 (weekends) that are the same value.

Has anyone any ideas on how to help ? Thanks .....