Task duration as a percentage of a predecessor

[Richard Millard]

Hi,

I have projects where certain tasks must be performed after an initial task
is completed. I am trying to create a template that can estimate the total
time it will take to complete the multiple tasks.

For example, Task B must follow Task A and typically takes 30% of the time
taken to complete Task A. Is it possible to set up a task so that it can
derive its duration as a percentage of the duration of its predecessor (or
of another linked task)?

Task A -> Task B
- if the Task A duration is set to 10 hours, Task B would automatically
calculate to an expected duration of 3 hours.

Thanks,

Richard

 

[John]

Hi,

I have projects where certain tasks must be performed after an initial task
is completed. I am trying to create a template that can estimate the total
time it will take to complete the multiple tasks.

For example, Task B must follow Task A and typically takes 30% of the time
taken to complete Task A. Is it possible to set up a task so that it can
derive its duration as a percentage of the duration of its predecessor (or
of another linked task)?

Task A -> Task B
- if the Task A duration is set to 10 hours, Task B would automatically
calculate to an expected duration of 3 hours.

Thanks,

Richard

Richard,
If you already know what the ratio is, why not simply set it up that
way? Duration is one of the fields that should be entered by the user
anyway.

Nonetheless there are a couple of ways to semi-automate what you want.
The first is to use a formula in a spare field (Duration1 might be a
good choice) to calculate the value you want. Then use a Paste Link to
link the spare field to the Duration field. Not the method I would
choose (due to the potential for corruption with paste links), but then
it should work ok if you are very careful and diligent with the links.

A better approach, in my opinion, would be to use a simple VBA macro to
adjust the duration of selected tasks. The advantage is that there is no
issue with corruption. The disadvantages are that the update will only
occur when the macro is run and simply writing the macro requires some
knowledge of VBA.

Hope this helps.
John
Project MVP