Create ASC and DESC INDEX in in one index

Question

I want to create an index (in Delphi/Interbase) which contained a ASC and a DESC order.

Example:

CREATE INDEX AMUT_DAT ON ARTIKMUT(DATUM,ARTIKEL,KODE);

This create DATUM and ARTIKEL ascending.

When I create it as follow:

CREATE DESCENDING INDEX AMUT_DAT ON ARTIKMUT(DATUM,ARTIKEL,KODE);

then the field DATUM is ASCENDING, but also the ARTIKEL. I want DATUM descending and ARTIKEL ascending.

I tried:

CREATE INDEX AMUT_DAT ON ARTIKMUT([DATUM] DESC,[ARTIKEL] ASC,[KODE] ASC);

But that does not work.

How can I create such an index in Interbase?