Britta --
You can fix or "lock" one of the three values in the Duration equation,
which are Duration, Work, or Units. This is known as the Task Type setting
for each task, and the Task Type can be either Fixed Units, Fixed Work, or
Fixed Duration. By default, the Task Type for each task is Fixed Units,
which explains the behavior you are seeing. When Units are fixed and you
change Duration, Work is recalculated automatically, and if you change Work
then Duration is recalculated. To fix either the Duration of Work values
for a single task, do the following:
1. Double-click the task in question
2. Click the Advanced tab
3. Set the Task Type value to either Fixed Work or Fixed Duration
4. Click OK
To set the Task Type for every task in a project, click the Select All
button in the upper left corner of the task sheet (blank gray button) to
select all tasks in the project. Click the Task Information button in the
middle of the Standard toolbar, and then complete steps 2-4 above. To set
the default Task Type for every task in every new project, do the following:
1. Open a blank project
2. Click Tools - Options
3. Select the Schedule tab
4. Set the Task Type to either Fixed Work or Fixed Duration
5. Click the Set as Default button
6. Click OK
7. Close and do not save the blank project
Another way of protecting your original Work and Duration values, as well as
the Start date and Finish date for each task is to baseline your project
before you begin entering progress. To do so, click Tools - Tracking - Save
Baseline and then click OK. The Baseline Duration, Baseline Work, Baseline
Start, and Baseline Finish values will reflect your original starting values
on each task, summary task, and for the project as a whole. As long as you
don't rebaseline the project, these values will not change. Hope this
explanation helps.
