Hi maurizio.rota,
I hate to cut and paste, but I think Workday() will help you:
From Help:
WORKDAY
See Also
Returns a number that represents a date that is the indicated number of working days before or after a date (the starting date). Working days exclude weekends and any dates identified as holidays. Use WORKDAY to exclude weekends or holidays when you calculate invoice due dates, expected delivery times, or the number of days of work performed. To view the number as a date, click Cells on the Format menu, click Date in the Category box, and then click a date format in the Type box.
If this function is not available, run the Setup program to install the Analysis ToolPak. After you install the Analysis ToolPak, you must enable it by using the Add-Ins command on the Tools menu.
How?
Syntax
WORKDAY(start_date,days,holidays)
Start_date is a date that represents the start date. Dates may be entered as text strings within quotation marks (for example, "1/30/1998" or "1998/01/30"), as serial numbers (for example, 35825, which represents January 30, 1998, if you're using the 1900 date system), or as results of other formulas or functions (for example, DATEVALUE("1/30/1998"))
Days is the number of nonweekend and nonholiday days before or after start_date. A positive value for days yields a future date; a negative value yields a past date.
Holidays is an optional list of one or more dates to exclude from the working calendar, such as state and federal holidays and floating holidays. The list can be either a range of cells that contain the dates or an array constant of the serial numbers that represent the dates. Learn about array constants. For more information about how Microsoft Excel uses serial numbers for dates, see the Remarks section.
Remarks
Excel stores dates as sequential serial numbers so that it can perform calculations on them. Excel stores January 1, 1900, as serial number 1 if your workbook uses the 1900 date system. If your workbook uses the 1904 date system, Excel stores January 1, 1904, as serial number 0 (January 2, 1904, is serial number 1). For example, in the 1900 date system, Excel stores January 1, 1998, as serial number 35796 because it is 35,795 days after January 1, 1900. Learn more about how Microsoft Excel stores dates and times.
If start_date is not a valid date, WORKDAY returns the #NUM! error value.
If start_date plus days yields an invalid date, WORKDAY returns the #NUM! error value.
If days is not an integer, it is truncated.
Examples
WORKDAY(DATEVALUE("01/03/1998"),5) equals 35804 or January 9, 1998.
If January 7, 1998, and January 8, 1998, are holidays, then:
WORKDAY(DATEVALUE("01/03/1998"),5,{35802,35803}) equals 35808 or January 13, 1998.
You can nest this in Text(string,format) with format something like "DD/MM/YY" for the format you wanted.
Hope this helps,
