master-detail relationship with dBase expression index

Hi,

I've been struggling with the following problem: I'd like to create a
master-detail relationship between to tables (TTable components, using
dBase files), so that the detail table is indexed with a dBase
expression index. Like this:

Master table: Customer table, index = CustomerID
Detail table: Customer activities, index = CustomerID +
DTOS(ActivityDate)

It doesn't seem to be possible to link these two tables using the
TTable.MasterSource and TTable.MasterFields properties, because these
won't work with an expression index. Any ideas?
There is no problem obviously, if the detail table is indexed only on
1 field (CustomerID), but then the detail rows will be in the order
they were added instead of e.g. chronological order (ActivityDate
field).

dBase expression indexes are widely used and Delphi seems to have
pretty good support for dBase databases. Is it really true, that
expression index is not supported by many of the TTable porperties and
methods (any method or property that takes field values or names as
arguments, like MasterFields & FindKey)? What am I missing?

The problem described can be worked around by using SQL query for
getting the detail dataset and sorting it by the ActivityDate field,
but to be able to edit it, there must be a Field index on the
ActivityDate field for the dBase table, otherwise the query result set
can not be live.

Sorry about the long description, but I'd really appreciate any input!

Thanks,

Jussi Koivumaa