The events are not triggered for a number of circumstances. This is
apparently one of them.
Not much you can do but change the way you are importing.
For example you could write your own import routine if you want it to only
bring over certain data or change values.
It wouldn't be much more difficult than trapping the before task change
event.
VBA help tells me this:
--------------------------
Remarks
Microsoft Project events do not occur when the project is embedded in
another document or application.
The ProjectBeforeTaskChange event doesn't occur when timescaled data
changes, when constraint data in the Task Details Form changes, when a task
is split by manipulating its task bar on the Gantt Chart, when changes are
made to outline level or outline number, when a baseline is saved, when a
baseline is cleared, when an entire task row is pasted, during resource pool
operations, when inserting or removing a subproject, or when changes have
been made using a custom form.
