Floating task durations based on a constraint for the last linkedtask

[rdemyan]

I have say 7 tasks. The first six should start on the same day and
have a floating duration that depends on the last task.

So I would like to have the first six tasks begin on say 4/21/08.
These six tasks are linked to the last task. The last task begins
when the other six are completed, but the last task will have a
constraint that it must be completed by 5/15/08.

Now if I change the last task constraint date from 5/15/08 to 5/14/08,
I would like the other six tasks to have their durations reduced by 1
day. MS Project keeps giving me a conflict message and it won't
reduce the durations of the other six tasks by 1 day.

So how do I accomplish something like this. This is routine in our
business. We have a start date and an estimated end date. Then the
client changes the end date and we need to see how that affects all of
the linked tasks between the start date and the end date. But I can't
seem to get MS Project to change the durations.

Thanks.

 

[John]

I have say 7 tasks. The first six should start on the same day and
have a floating duration that depends on the last task.

So I would like to have the first six tasks begin on say 4/21/08.
These six tasks are linked to the last task. The last task begins
when the other six are completed, but the last task will have a
constraint that it must be completed by 5/15/08.

Now if I change the last task constraint date from 5/15/08 to 5/14/08,
I would like the other six tasks to have their durations reduced by 1
day. MS Project keeps giving me a conflict message and it won't
reduce the durations of the other six tasks by 1 day.

So how do I accomplish something like this. This is routine in our
business. We have a start date and an estimated end date. Then the
client changes the end date and we need to see how that affects all of
the linked tasks between the start date and the end date. But I can't
seem to get MS Project to change the durations.

Thanks.

rdemyan,
There are several issues with the scenario you describe. First, you are
trying to "force the schedule". That's not how Project or even good
schedule management works. Second, duration is simply a measurement of
time, it is NOT a measurement of how much effort is required to actually
accomplish anything. Third, setting a fixed constraint, (e.g. must
finish by), on any task is not a good idea and to be honest, very few
things in life MUST be done by a particular date. I know, many people
will take issue with that but they are ignoring the flexibility offered
by negotiation and compromise among the affected parties. What? Did I
just say that? This must be a political year.

Ok, here's what should be doing. Lay out the first six tasks all
starting at the same time with a finish to start link to the 7th task,
presumably the customer's desired end task. Do not set a constraint on
any tasks. Instead, use the Deadline field to set a marker for the
completion of the last task - it will show up on the Gantt display as a
marker.

As far as the schedule itself is concerned, the length of time it takes
to accomplish a group of tasks is defined by the work content of those
tasks. That is, how many hours are estimated for each task. Remember,
Duration and work are two separate entities in Project. Work combined
with the number of resources assigned to a task will determine how long,
(i.e. duration), it will take to finish the task. That then defines the
schedule. If the client needs to move the finish date up, you must
review the plan and determine where you can pull the schedule in by, a)
assigning additional resources to lagging tasks, b) adjust the Remaining
Work field, if possible, or c) sit down with the client and let them
know what will be impacted by the tighter schedule.

And by the way, Project will not "adjust" the duration when the user
changes the end date. Duration is recalculated based on adjustments to
the schedule described above.

Hope this helps.
John
Project MVP