I wish to edit the calendar used in excel to exclude weekends
 

I have an excel file that i use to forecast when certain actions are due to
be completed based on the working days it takes to process each action. I
wish to only display dates during the working week that are not public
holidays or during christmas leave. For example if I plan on having an action
complete on Monday the 5th and the next action takes 7 working days to
process it should be scheduled for completion on Wednesday the 14th, it is
not necessary for the days of the week to be displayed however