Workday and Networkday - Cascading dependencies

Hi,

I've been asked to replicate a a system a colleague has seen called Workfront.

The system works by setting a delivery date and then all previous tasks cascade backwards to create a start date. You can then amend duration etc to fit your timeframe.
Both workday and network day work up to a point but you have to amend each duration rather than just the delivery date.
On the attached workbook the attempt with network day and the SUM formula understandably messes with the networkday formula and returns weekend days.

Is there a way of achieving this, I was thinking something along the lines of adding a calendar along with some kind of formula?

Happy to do the leg work myself I just need pointing in the correct direction.

many thanks

Try in C4: =WORKDAY(C5,-B4), copy down to C10.

Thanks Joseph, you might have to show me as I'm not getting a result just NUM.

Attach your workbook showing the error.

You may have already noticed there is a 1 day difference between WORKDAY and NETWORKDAYS as NETWORKDAYS include both the Start Date and End Date in its count.

You will get a NUM error if you copy all the way down to C11 (if you double-click the cell in C4, it will copy down to C11 and give you a NUM error). If you copy down and stop at C10, you should not get a NUM error.

Thanks Joseph, I've had another go and all works as you described. Thanks for your help.