Hi, davinosky!
If you want to get displayed Monday, Tuesday, ..., you can just format the cell (Ctrl-1, Custom, and enter dddd as value). If you want to retrieve the number of day within the week you can use the WEEKDAY function: WEEKDAY(date,type), where type indicates if Monday=0, or 1, or where week starts (you can access the built-in Excel help by clicking in the "f(x)" icon at the left of the edit bar).
Regards!