How do I calculate dates backwards from a project end date

[Guest]

In using Excel 2003 I am trying to build a schedule, starting backwards and
determining due dates based on timeframes, i.e. 6 months from completion
date, 3 months from completion date, 6 weeks from completion date, etc. I am
also trying to incorporate NETWORKDAYS minus holidays.

Any help would be appreciated.

Kathy

 

[Bob Phillips]

Use Workdays with a negative number of days

=WORKDAY(A1,-30,holidays)

where holidays is a named range of holiday dates